[BreakFalseDeps] ignore function with minsize attribute

This came up in the x86-specific:
https://bugs.llvm.org/show_bug.cgi?id=43239
...but it is a general problem for the BreakFalseDeps pass.
Dependencies may be broken by adding some other instruction,
so that should be avoided if the overall goal is to minimize size.

Differential Revision: https://reviews.llvm.org/D67363

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@372628 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/BreakFalseDeps.cpp b/lib/CodeGen/BreakFalseDeps.cpp
index 382f76da3218c2352f58369d09b1db0e0b521342..9b6da64e043b02da2652b08a5d17be8c4360c32a 100644 (file)
--- a/lib/CodeGen/BreakFalseDeps.cpp
+++ b/lib/CodeGen/BreakFalseDeps.cpp
@@ -177,6 +177,7 @@ void BreakFalseDeps::processDefs(MachineInstr *MI) {
   assert(!MI->isDebugInstr() && "Won't process debug values");
 
   // Break dependence on undef uses. Do this before updating LiveRegs below.
+  // This can remove a false dependence with no additional instructions.
   unsigned OpNum;
   unsigned Pref = TII->getUndefRegClearance(*MI, OpNum, TRI);
   if (Pref) {
@@ -188,6 +189,11 @@ void BreakFalseDeps::processDefs(MachineInstr *MI) {
       UndefReads.push_back(std::make_pair(MI, OpNum));
   }
 
+  // The code below allows the target to create a new instruction to break the
+  // dependence. That opposes the goal of minimizing size, so bail out now.
+  if (MF->getFunction().hasMinSize())
+    return;
+
   const MCInstrDesc &MCID = MI->getDesc();
   for (unsigned i = 0,
     e = MI->isVariadic() ? MI->getNumOperands() : MCID.getNumDefs();
@@ -208,6 +214,11 @@ void BreakFalseDeps::processUndefReads(MachineBasicBlock *MBB) {
   if (UndefReads.empty())
     return;
 
+  // The code below allows the target to create a new instruction to break the
+  // dependence. That opposes the goal of minimizing size, so bail out now.
+  if (MF->getFunction().hasMinSize())
+    return;
+
   // Collect this block's live out register units.
   LiveRegSet.init(*TRI);
   // We do not need to care about pristine registers as they are just preserved

diff --git a/test/CodeGen/ARM/a15-partial-update.ll b/test/CodeGen/ARM/a15-partial-update.ll
index c20aaa2fa5dd86c690d5a6c885379123773df083..a3971d6a034bf0ef4fce32d76656a54f438d6372 100644 (file)
--- a/test/CodeGen/ARM/a15-partial-update.ll
+++ b/test/CodeGen/ARM/a15-partial-update.ll
@@ -56,6 +56,11 @@ ret:
   ret void
 }
 
+; If minimizing size, that overrides perf, so no extra vmov.f64 here.
+
+; TODO: This (and above) could use a splat load to remove the false
+;       dependence with no extra instruction.
+
 define void @t2_minsize(<4 x i8> *%in, <4 x i8> *%out, i32 %n) minsize {
 ; CHECK-LABEL: t2_minsize:
 ; CHECK:       @ %bb.0: @ %entry
@@ -63,7 +68,6 @@ define void @t2_minsize(<4 x i8> *%in, <4 x i8> *%out, i32 %n) minsize {
 ; CHECK-NEXT:    add r1, r1, #4
 ; CHECK-NEXT:  .LBB2_1: @ %loop
 ; CHECK-NEXT:    @ =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    vmov.f64 d16, #5.000000e-01
 ; CHECK-NEXT:    vld1.32 {d16[0]}, [r0:32]
 ; CHECK-NEXT:    vmovl.u8 q8, d16
 ; CHECK-NEXT:    vuzp.8 d16, d18

diff --git a/test/CodeGen/X86/sqrt-partial.ll b/test/CodeGen/X86/sqrt-partial.ll
index d017b5c360085161896e048658b692ea03e90eb7..7ed68c1084998ef4d0a131c4f70116004ffb143a 100644 (file)
--- a/test/CodeGen/X86/sqrt-partial.ll
+++ b/test/CodeGen/X86/sqrt-partial.ll
@@ -67,7 +67,6 @@ define double @minsize(double %x, double %y) minsize {
 ; SSE-NEXT:    mulsd %xmm0, %xmm0
 ; SSE-NEXT:    mulsd %xmm1, %xmm1
 ; SSE-NEXT:    addsd %xmm0, %xmm1
-; SSE-NEXT:    xorps %xmm0, %xmm0
 ; SSE-NEXT:    sqrtsd %xmm1, %xmm0
 ; SSE-NEXT:    retq
 ;

diff --git a/test/CodeGen/X86/stack-folding-fp-avx1.ll b/test/CodeGen/X86/stack-folding-fp-avx1.ll
index 3b69f2d9c524fec8b941d0a6b63da43ace03d032..6625cc4f07a27971f63442f14657e22883af5b88 100644 (file)
--- a/test/CodeGen/X86/stack-folding-fp-avx1.ll
+++ b/test/CodeGen/X86/stack-folding-fp-avx1.ll
@@ -2876,7 +2876,6 @@ define double @stack_fold_roundsd_minsize(double %a0) minsize {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    vxorps %xmm0, %xmm0, %xmm0
 ; CHECK-NEXT:    vroundsd $9, {{[-0-9]+}}(%r{{[sb]}}p), %xmm0, %xmm0 # 8-byte Folded Reload
 ; CHECK-NEXT:    retq
   %1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()

diff --git a/test/CodeGen/X86/stack-folding-fp-sse42.ll b/test/CodeGen/X86/stack-folding-fp-sse42.ll
index 0c81f1ac73a459347b40a632b103c7de77d73892..306ee3109809015709143622bc4bcb7365ae5f73 100644 (file)
--- a/test/CodeGen/X86/stack-folding-fp-sse42.ll
+++ b/test/CodeGen/X86/stack-folding-fp-sse42.ll
@@ -583,7 +583,6 @@ define float @stack_fold_cvtsd2ss(double %a0) minsize {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    xorps %xmm0, %xmm0
 ; CHECK-NEXT:    cvtsd2ss {{[-0-9]+}}(%r{{[sb]}}p), %xmm0 # 8-byte Folded Reload
 ; CHECK-NEXT:    retq
   %1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()
@@ -975,7 +974,6 @@ define double @stack_fold_cvtss2sd(float %a0) minsize {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    xorps %xmm0, %xmm0
 ; CHECK-NEXT:    cvtss2sd {{[-0-9]+}}(%r{{[sb]}}p), %xmm0 # 4-byte Folded Reload
 ; CHECK-NEXT:    retq
   %1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()
@@ -2012,7 +2010,6 @@ define float @stack_fold_roundss(float %a0) minsize {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    xorps %xmm0, %xmm0
 ; CHECK-NEXT:    roundss $9, {{[-0-9]+}}(%r{{[sb]}}p), %xmm0 # 4-byte Folded Reload
 ; CHECK-NEXT:    retq
   %1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()
@@ -2181,7 +2178,6 @@ define float @stack_fold_sqrtss(float %a0) minsize {
 ; CHECK-NEXT:    #APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    xorps %xmm0, %xmm0
 ; CHECK-NEXT:    sqrtss {{[-0-9]+}}(%r{{[sb]}}p), %xmm0 # 4-byte Folded Reload
 ; CHECK-NEXT:    retq
   %1 = tail call <2 x i64> asm sideeffect "nop", "=x,~{xmm1},~{xmm2},~{xmm3},~{xmm4},~{xmm5},~{xmm6},~{xmm7},~{xmm8},~{xmm9},~{xmm10},~{xmm11},~{xmm12},~{xmm13},~{xmm14},~{xmm15},~{flags}"()