[X86] Add test case to show failure to combine away negates that may be created by...

Mul by constant can expand to a sequence that ends with a negate. If the next instruction is an add or sub we might be able to fold the negate away.

We currently fail to do this because we explicitly don't add anything to the DAG combine worklist when we expand multiplies. This is primarily to keep the multipy from being reformed, but we should consider adding the users to worklist.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337843 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/CodeGen/X86/mul-constant-i32.ll b/test/CodeGen/X86/mul-constant-i32.ll
index 7dd7a7a7ad68dc633cea53d2eceb7d5c42527fa6..d80e69dd61bab43c2c5f46e206e541cd006c6e8b 100644 (file)
--- a/test/CodeGen/X86/mul-constant-i32.ll
+++ b/test/CodeGen/X86/mul-constant-i32.ll
@@ -1748,3 +1748,67 @@ define i32 @test_mul_spec(i32 %x) nounwind {
   %mul3 = mul nsw i32 %add, %add2
   ret i32 %mul3
 }
+
+; This makes sure we are able to fold the negate generated by the mul expansion
+; into the next instruction.
+; FIXME: We make this work.
+define i32 @mul_neg_fold(i32 %a, i32 %b) {
+; X86-LABEL: mul_neg_fold:
+; X86:       # %bb.0:
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    leal (%eax,%eax,8), %eax
+; X86-NEXT:    negl %eax
+; X86-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    retl
+;
+; X64-HSW-LABEL: mul_neg_fold:
+; X64-HSW:       # %bb.0:
+; X64-HSW-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-HSW-NEXT:    leal (%rdi,%rdi,8), %eax # sched: [1:0.50]
+; X64-HSW-NEXT:    negl %eax # sched: [1:0.25]
+; X64-HSW-NEXT:    addl %esi, %eax # sched: [1:0.25]
+; X64-HSW-NEXT:    retq # sched: [7:1.00]
+;
+; X64-JAG-LABEL: mul_neg_fold:
+; X64-JAG:       # %bb.0:
+; X64-JAG-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-JAG-NEXT:    leal (%rdi,%rdi,8), %eax # sched: [2:1.00]
+; X64-JAG-NEXT:    negl %eax # sched: [1:0.50]
+; X64-JAG-NEXT:    addl %esi, %eax # sched: [1:0.50]
+; X64-JAG-NEXT:    retq # sched: [4:1.00]
+;
+; X86-NOOPT-LABEL: mul_neg_fold:
+; X86-NOOPT:       # %bb.0:
+; X86-NOOPT-NEXT:    imull $-9, {{[0-9]+}}(%esp), %eax
+; X86-NOOPT-NEXT:    addl {{[0-9]+}}(%esp), %eax
+; X86-NOOPT-NEXT:    retl
+;
+; HSW-NOOPT-LABEL: mul_neg_fold:
+; HSW-NOOPT:       # %bb.0:
+; HSW-NOOPT-NEXT:    imull $-9, %edi, %eax # sched: [3:1.00]
+; HSW-NOOPT-NEXT:    addl %esi, %eax # sched: [1:0.25]
+; HSW-NOOPT-NEXT:    retq # sched: [7:1.00]
+;
+; JAG-NOOPT-LABEL: mul_neg_fold:
+; JAG-NOOPT:       # %bb.0:
+; JAG-NOOPT-NEXT:    imull $-9, %edi, %eax # sched: [3:1.00]
+; JAG-NOOPT-NEXT:    addl %esi, %eax # sched: [1:0.50]
+; JAG-NOOPT-NEXT:    retq # sched: [4:1.00]
+;
+; X64-SLM-LABEL: mul_neg_fold:
+; X64-SLM:       # %bb.0:
+; X64-SLM-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-SLM-NEXT:    leal (%rdi,%rdi,8), %eax # sched: [1:1.00]
+; X64-SLM-NEXT:    negl %eax # sched: [1:0.50]
+; X64-SLM-NEXT:    addl %esi, %eax # sched: [1:0.50]
+; X64-SLM-NEXT:    retq # sched: [4:1.00]
+;
+; SLM-NOOPT-LABEL: mul_neg_fold:
+; SLM-NOOPT:       # %bb.0:
+; SLM-NOOPT-NEXT:    imull $-9, %edi, %eax # sched: [3:1.00]
+; SLM-NOOPT-NEXT:    addl %esi, %eax # sched: [1:0.50]
+; SLM-NOOPT-NEXT:    retq # sched: [4:1.00]
+  %c = mul i32 %a, -9
+  %d = add i32 %b, %c
+  ret i32 %d
+}