From: Tim Northover <tnorthover@apple.com>
Date: Tue, 6 Aug 2019 09:18:41 +0000 (+0000)
Subject: AArch64: use xzr/wzr for constant 0 in GlobalISel.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e9b35ac319a47075342e117fa6a53b50278a9909;p=llvm

AArch64: use xzr/wzr for constant 0 in GlobalISel.

COPYs from xzr and wzr can often be folded away entirely during register
allocation, unlike a movz.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368003 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/AArch64/AArch64InstructionSelector.cpp b/lib/Target/AArch64/AArch64InstructionSelector.cpp
index a2f51415b75..59cfcca3157 100644
--- a/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -1284,6 +1284,31 @@ bool AArch64InstructionSelector::earlySelect(MachineInstr &I) const {
     return earlySelectSHL(I, MRI);
   case TargetOpcode::G_LOAD:
     return earlySelectLoad(I, MRI);
+  case TargetOpcode::G_CONSTANT: {
+    bool IsZero = false;
+    if (I.getOperand(1).isCImm())
+      IsZero = I.getOperand(1).getCImm()->getZExtValue() == 0;
+    else if (I.getOperand(1).isImm())
+      IsZero = I.getOperand(1).getImm() == 0;
+
+    if (!IsZero)
+      return false;
+
+    Register DefReg = I.getOperand(0).getReg();
+    LLT Ty = MRI.getType(DefReg);
+    assert((Ty == LLT::scalar(64) || Ty == LLT::scalar(32)) &&
+           "Unexpected legal constant type");
+
+    if (Ty == LLT::scalar(64)) {
+      I.getOperand(1).ChangeToRegister(AArch64::XZR, false);
+      RBI.constrainGenericRegister(DefReg, AArch64::GPR64RegClass, MRI);
+    } else {
+      I.getOperand(1).ChangeToRegister(AArch64::WZR, false);
+      RBI.constrainGenericRegister(DefReg, AArch64::GPR32RegClass, MRI);
+    }
+    I.setDesc(TII.get(TargetOpcode::COPY));
+    return true;
+  }
   default:
     return false;
   }
diff --git a/test/CodeGen/AArch64/GlobalISel/fold-select.mir b/test/CodeGen/AArch64/GlobalISel/fold-select.mir
index 1e16d86dd1f..53bf0a32af4 100644
--- a/test/CodeGen/AArch64/GlobalISel/fold-select.mir
+++ b/test/CodeGen/AArch64/GlobalISel/fold-select.mir
@@ -21,9 +21,9 @@ body:             |
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32sp = COPY $w0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVwzr:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: $wzr = SUBSWri [[COPY]], 0, 0, implicit-def $nzcv
-    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm]], [[COPY1]], 0, implicit $nzcv
+    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVwzr]], [[COPY1]], 0, implicit $nzcv
     ; CHECK: $w0 = COPY [[CSELWr]]
     ; CHECK: RET_ReallyLR implicit $w0
     %0:gpr(s32) = COPY $w0
@@ -50,9 +50,9 @@ body:             |
     ; CHECK: liveins: $s0, $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w1
     ; CHECK: [[COPY1:%[0-9]+]]:fpr32 = COPY $s0
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVwzr:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: FCMPSri [[COPY1]], implicit-def $nzcv
-    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm]], [[COPY]], 0, implicit $nzcv
+    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVwzr]], [[COPY]], 0, implicit $nzcv
     ; CHECK: $w0 = COPY [[CSELWr]]
     ; CHECK: RET_ReallyLR implicit $w0
     %1:gpr(s32) = COPY $w1
diff --git a/test/CodeGen/AArch64/GlobalISel/opt-fold-compare.mir b/test/CodeGen/AArch64/GlobalISel/opt-fold-compare.mir
index c080db05972..c81a10cb0e7 100644
--- a/test/CodeGen/AArch64/GlobalISel/opt-fold-compare.mir
+++ b/test/CodeGen/AArch64/GlobalISel/opt-fold-compare.mir
@@ -44,10 +44,10 @@ body:             |
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVwzr:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: $wzr = ADDSWrr [[COPY]], [[COPY1]], implicit-def $nzcv
-    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm1]], [[MOVi32imm]], 1, implicit $nzcv
+    ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm1]], [[MOVwzr]], 1, implicit $nzcv
     ; CHECK: $w0 = COPY [[CSELWr]]
     ; CHECK: RET_ReallyLR implicit $w0
     %0:gpr(s32) = COPY $w0
@@ -76,7 +76,7 @@ body:             |
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: $wzr = ADDSWrr [[COPY]], [[COPY1]], implicit-def $nzcv
     ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm1]], [[MOVi32imm]], 1, implicit $nzcv
@@ -108,7 +108,7 @@ body:             |
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: [[SUBSWrr:%[0-9]+]]:gpr32 = SUBSWrr [[MOVi32imm]], [[COPY1]], implicit-def $nzcv
     ; CHECK: $wzr = SUBSWrr [[COPY]], [[SUBSWrr]], implicit-def $nzcv
@@ -141,7 +141,7 @@ body:             |
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: [[SUBSWrr:%[0-9]+]]:gpr32 = SUBSWrr [[MOVi32imm]], [[COPY]], implicit-def $nzcv
     ; CHECK: $wzr = SUBSWrr [[SUBSWrr]], [[COPY1]], implicit-def $nzcv
@@ -174,7 +174,7 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: [[COPY:%[0-9]+]]:gpr64 = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr64 = COPY $x1
-    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[MOVi64imm1:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: $xzr = ADDSXrr [[COPY]], [[COPY1]], implicit-def $nzcv
     ; CHECK: [[CSELXr:%[0-9]+]]:gpr64 = CSELXr [[MOVi64imm1]], [[MOVi64imm]], 1, implicit $nzcv
@@ -206,7 +206,7 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: [[COPY:%[0-9]+]]:gpr64 = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr64 = COPY $x1
-    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[MOVi64imm1:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: $xzr = ADDSXrr [[COPY]], [[COPY1]], implicit-def $nzcv
     ; CHECK: [[CSELXr:%[0-9]+]]:gpr64 = CSELXr [[MOVi64imm1]], [[MOVi64imm]], 1, implicit $nzcv
@@ -238,7 +238,7 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: [[COPY:%[0-9]+]]:gpr64 = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr64 = COPY $x1
-    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[MOVi64imm1:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: [[SUBSXrr:%[0-9]+]]:gpr64 = SUBSXrr [[MOVi64imm]], [[COPY1]], implicit-def $nzcv
     ; CHECK: $xzr = SUBSXrr [[COPY]], [[SUBSXrr]], implicit-def $nzcv
@@ -271,7 +271,7 @@ body:             |
     ; CHECK: liveins: $x0, $x1
     ; CHECK: [[COPY:%[0-9]+]]:gpr64 = COPY $x0
     ; CHECK: [[COPY1:%[0-9]+]]:gpr64 = COPY $x1
-    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[MOVi64imm1:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: [[SUBSXrr:%[0-9]+]]:gpr64 = SUBSXrr [[MOVi64imm]], [[COPY]], implicit-def $nzcv
     ; CHECK: $xzr = SUBSXrr [[SUBSXrr]], [[COPY1]], implicit-def $nzcv
@@ -302,7 +302,7 @@ body:             |
     ; CHECK-LABEL: name: tst_s32
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: $wzr = ANDSWrr [[MOVi32imm]], [[COPY]], implicit-def $nzcv
     ; CHECK: [[CSELWr:%[0-9]+]]:gpr32 = CSELWr [[MOVi32imm1]], [[MOVi32imm]], 0, implicit $nzcv
@@ -333,7 +333,7 @@ body:             |
     ; CHECK-LABEL: name: tst_s64
     ; CHECK: liveins: $x0, $x1
     ; CHECK: [[COPY:%[0-9]+]]:gpr64 = COPY $x1
-    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[MOVi64imm:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[MOVi64imm1:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: $xzr = ANDSXrr [[MOVi64imm]], [[COPY]], implicit-def $nzcv
     ; CHECK: [[CSELXr:%[0-9]+]]:gpr64 = CSELXr [[MOVi64imm1]], [[MOVi64imm]], 0, implicit $nzcv
@@ -364,7 +364,7 @@ body:             |
     ; CHECK-LABEL: name: no_tst_unsigned_compare
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: [[ANDWrr:%[0-9]+]]:gpr32common = ANDWrr [[MOVi32imm]], [[COPY]]
     ; CHECK: $wzr = SUBSWri [[ANDWrr]], 0, 0, implicit-def $nzcv
@@ -396,7 +396,7 @@ body:             |
     ; CHECK-LABEL: name: no_tst_nonzero
     ; CHECK: liveins: $w0, $w1
     ; CHECK: [[COPY:%[0-9]+]]:gpr32 = COPY $w1
-    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: [[ANDWrr:%[0-9]+]]:gpr32common = ANDWrr [[MOVi32imm]], [[COPY]]
     ; CHECK: $wzr = SUBSWri [[ANDWrr]], 42, 0, implicit-def $nzcv
diff --git a/test/CodeGen/AArch64/GlobalISel/select-cmpxchg.mir b/test/CodeGen/AArch64/GlobalISel/select-cmpxchg.mir
index 345c21d18fd..84713713467 100644
--- a/test/CodeGen/AArch64/GlobalISel/select-cmpxchg.mir
+++ b/test/CodeGen/AArch64/GlobalISel/select-cmpxchg.mir
@@ -19,7 +19,7 @@ body:             |
 
     ; CHECK-LABEL: name: cmpxchg_i32
     ; CHECK: [[COPY:%[0-9]+]]:gpr64sp = COPY $x0
-    ; CHECK: [[CMP:%[0-9]+]]:gpr32 = MOVi32imm 0
+    ; CHECK: [[CMP:%[0-9]+]]:gpr32 = COPY $wzr
     ; CHECK: [[CST:%[0-9]+]]:gpr32 = MOVi32imm 1
     ; CHECK: [[RES:%[0-9]+]]:gpr32 = CASW [[CMP]], [[CST]], [[COPY]] :: (load store monotonic 4 on %ir.addr)
     ; CHECK: $w0 = COPY [[RES]]
@@ -41,7 +41,7 @@ body:             |
 
     ; CHECK-LABEL: name: cmpxchg_i64
     ; CHECK: [[COPY:%[0-9]+]]:gpr64sp = COPY $x0
-    ; CHECK: [[CMP:%[0-9]+]]:gpr64 = MOVi64imm 0
+    ; CHECK: [[CMP:%[0-9]+]]:gpr64 = COPY $xzr
     ; CHECK: [[CST:%[0-9]+]]:gpr64 = MOVi64imm 1
     ; CHECK: [[RES:%[0-9]+]]:gpr64 = CASX [[CMP]], [[CST]], [[COPY]] :: (load store monotonic 8 on %ir.addr)
     ; CHECK: $x0 = COPY [[RES]]
diff --git a/test/CodeGen/AArch64/GlobalISel/select-jump-table-brjt.mir b/test/CodeGen/AArch64/GlobalISel/select-jump-table-brjt.mir
index bf71804af34..8098fe34269 100644
--- a/test/CodeGen/AArch64/GlobalISel/select-jump-table-brjt.mir
+++ b/test/CodeGen/AArch64/GlobalISel/select-jump-table-brjt.mir
@@ -57,7 +57,7 @@ body:             |
   ; CHECK:   successors: %bb.4(0x40000000), %bb.1(0x40000000)
   ; CHECK:   liveins: $w0
   ; CHECK:   [[COPY:%[0-9]+]]:gpr32common = COPY $w0
-  ; CHECK:   [[MOVi32imm:%[0-9]+]]:gpr32 = MOVi32imm 0
+  ; CHECK:   [[MOVi32imm:%[0-9]+]]:gpr32 = COPY $wzr
   ; CHECK:   [[SUBSWri:%[0-9]+]]:gpr32 = SUBSWri [[COPY]], 4, 0, implicit-def $nzcv
   ; CHECK:   [[SUBREG_TO_REG:%[0-9]+]]:gpr64 = SUBREG_TO_REG 0, [[SUBSWri]], %subreg.sub_32
   ; CHECK:   [[UBFMXri:%[0-9]+]]:gpr64common = UBFMXri [[SUBREG_TO_REG]], 0, 31
@@ -65,7 +65,7 @@ body:             |
   ; CHECK:   Bcc 8, %bb.4, implicit $nzcv
   ; CHECK: bb.1.entry:
   ; CHECK:   successors: %bb.3(0x2aaaaaab), %bb.4(0x2aaaaaab), %bb.2(0x2aaaaaab)
-  ; CHECK:   [[MOVi32imm1:%[0-9]+]]:gpr32 = MOVi32imm 0
+  ; CHECK:   [[MOVi32imm1:%[0-9]+]]:gpr32 = COPY $wzr
   ; CHECK:   [[MOVaddrJT:%[0-9]+]]:gpr64 = MOVaddrJT target-flags(aarch64-page) %jump-table.0, target-flags(aarch64-pageoff, aarch64-nc) %jump-table.0
   ; CHECK:   early-clobber %18:gpr64, early-clobber %19:gpr64sp = JumpTableDest32 [[MOVaddrJT]], [[UBFMXri]], %jump-table.0
   ; CHECK:   BR %18
diff --git a/test/CodeGen/AArch64/GlobalISel/swifterror.ll b/test/CodeGen/AArch64/GlobalISel/swifterror.ll
index 81ec474b641..d549d22316b 100644
--- a/test/CodeGen/AArch64/GlobalISel/swifterror.ll
+++ b/test/CodeGen/AArch64/GlobalISel/swifterror.ll
@@ -59,7 +59,7 @@ define float @caller2(i8* %error_ref) {
 ; CHECK-LABEL: caller2:
 ; CHECK: mov [[ID:x[0-9]+]], x0
 ; CHECK: fmov [[CMP:s[0-9]+]], #1.0
-; CHECK: mov x21, #0
+; CHECK: mov x21, xzr
 ; CHECK: bl {{.*}}foo
 ; CHECK: cbnz x21
 ; CHECK: fcmp s0, [[CMP]]
@@ -187,7 +187,7 @@ entry:
 define float @caller3(i8* %error_ref) {
 ; CHECK-LABEL: caller3:
 ; CHECK: mov [[ID:x[0-9]+]], x0
-; CHECK: mov [[ZERO:x[0-9]+]], #0
+; CHECK: mov [[ZERO:x[0-9]+]], xzr
 ; CHECK: bl {{.*}}foo_sret
 ; CHECK: mov x0, x21
 ; CHECK: cbnz x21
@@ -263,8 +263,8 @@ define float @caller4(i8* %error_ref) {
 
 ; CHECK: mov [[ID:x[0-9]+]], x0
 ; CHECK: stp {{x[0-9]+}}, {{x[0-9]+}}, [sp]
-; CHECK: mov x21, #0
 ; CHECK: str {{x[0-9]+}}, [sp, #16]
+; CHECK: mov x21, xzr
 
 ; CHECK: bl {{.*}}foo_vararg
 ; CHECK: mov x0, x21
@@ -333,7 +333,6 @@ entry:
 ; CHECK:  mov      x27, x7
 ; CHECK:  mov      x28, x21
 ; Setup call.
-; CHECK:  mov     x8, #0
 ; CHECK:  mov     x0, #1
 ; CHECK:  mov     x1, #2
 ; CHECK:  mov     x2, #3
@@ -342,7 +341,8 @@ entry:
 ; CHECK:  mov     x5, #6
 ; CHECK:  mov     x6, #7
 ; CHECK:  mov     x7, #8
-; CHECK:  mov      x21, #0
+; CHECK:  str     xzr, [sp]
+; CHECK:  mov      x21, xzr
 ; CHECK:  bl      _params_in_reg2
 ; Restore original arguments for next call.
 ; CHECK:  ldr      x0, [sp
@@ -406,7 +406,7 @@ declare swiftcc void @params_in_reg2(i64, i64, i64, i64, i64, i64, i64, i64, i8*
 ; CHECK:  mov     x5, #6
 ; CHECK:  mov     x6, #7
 ; CHECK:  mov     x7, #8
-; CHECK:  mov      x21, #0
+; CHECK:  mov      x21, xzr
 ; CHECK:  bl      _params_in_reg2
 ; Store swifterror %error_ptr_ref.
 ; CHECK:  stp     {{x[0-9]+}}, x21, [sp]
@@ -489,7 +489,7 @@ entry:
 
 declare swiftcc void @foo2(%swift_error** swifterror)
 ; CHECK-LABEL: testAssign
-; CHECK: mov      x21, #0
+; CHECK: mov      x21, xzr
 ; CHECK: bl      _foo2
 ; CHECK: mov      x0, x21