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-rw-r--r--llvm/lib/Target/X86/X86ISelLowering.cpp22
-rw-r--r--llvm/test/CodeGen/X86/imul.ll23
2 files changed, 23 insertions, 22 deletions
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ef8a6d68395..12f6d409a60 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -33922,14 +33922,20 @@ static SDValue combineMul(SDNode *N, SelectionDAG &DAG,
DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
DAG.getConstant(Log2_64(NumSign * SignMulAmt - 1), DL,
MVT::i8)));
+ // To negate, subtract the number from zero
+ if (SignMulAmt < 0)
+ NewMul = DAG.getNode(ISD::SUB, DL, VT,
+ DAG.getConstant(0, DL, VT), NewMul);
} else if (IsPowerOf2_64MinusOne) {
// (mul x, 2^N - 1) => (sub (shl x, N), x)
- NewMul = DAG.getNode(
- ISD::SUB, DL, VT,
- DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
- DAG.getConstant(Log2_64(NumSign * SignMulAmt + 1), DL,
- MVT::i8)),
- N->getOperand(0));
+ NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
+ DAG.getConstant(Log2_64(NumSign * SignMulAmt + 1),
+ DL, MVT::i8));
+ // To negate, reverse the operands of the subtract.
+ if (SignMulAmt < 0)
+ NewMul = DAG.getNode(ISD::SUB, DL, VT, N->getOperand(0), NewMul);
+ else
+ NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0));
} else if (IsPowerOf2_64MinusTwo && NumSign == 1) {
// (mul x, 2^N - 1) => (sub (shl x, N), x)
NewMul = DAG.getNode(ISD::SHL, DL, VT, N->getOperand(0),
@@ -33938,10 +33944,6 @@ static SDValue combineMul(SDNode *N, SelectionDAG &DAG,
NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0));
NewMul = DAG.getNode(ISD::SUB, DL, VT, NewMul, N->getOperand(0));
}
- // To negate, subtract the number from zero
- if (NewMul && NumSign == -1)
- NewMul =
- DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT), NewMul);
}
}
diff --git a/llvm/test/CodeGen/X86/imul.ll b/llvm/test/CodeGen/X86/imul.ll
index 761484c069b..14f15143b95 100644
--- a/llvm/test/CodeGen/X86/imul.ll
+++ b/llvm/test/CodeGen/X86/imul.ll
@@ -324,17 +324,16 @@ define i32 @test1(i32 %a) {
; X64: # %bb.0: # %entry
; X64-NEXT: movl %edi, %eax
; X64-NEXT: shll $5, %eax
-; X64-NEXT: subl %edi, %eax
-; X64-NEXT: negl %eax
+; X64-NEXT: subl %eax, %edi
+; X64-NEXT: movl %edi, %eax
; X64-NEXT: retq
;
; X86-LABEL: test1:
; X86: # %bb.0: # %entry
-; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
-; X86-NEXT: movl %ecx, %eax
-; X86-NEXT: shll $5, %eax
+; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT: movl %eax, %ecx
+; X86-NEXT: shll $5, %ecx
; X86-NEXT: subl %ecx, %eax
-; X86-NEXT: negl %eax
; X86-NEXT: retl
entry:
%tmp3 = mul i32 %a, -31
@@ -414,8 +413,8 @@ define i64 @test5(i64 %a) {
; X64: # %bb.0: # %entry
; X64-NEXT: movq %rdi, %rax
; X64-NEXT: shlq $5, %rax
-; X64-NEXT: subq %rdi, %rax
-; X64-NEXT: negq %rax
+; X64-NEXT: subq %rax, %rdi
+; X64-NEXT: movq %rdi, %rax
; X64-NEXT: retq
;
; X86-LABEL: test5:
@@ -424,15 +423,15 @@ define i64 @test5(i64 %a) {
; X86-NEXT: .cfi_def_cfa_offset 8
; X86-NEXT: .cfi_offset %esi, -8
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
-; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT: movl %eax, %esi
-; X86-NEXT: shll $5, %esi
+; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
+; X86-NEXT: movl %esi, %eax
+; X86-NEXT: shll $5, %eax
; X86-NEXT: subl %eax, %esi
; X86-NEXT: movl $-31, %edx
; X86-NEXT: movl %ecx, %eax
; X86-NEXT: mull %edx
; X86-NEXT: subl %ecx, %edx
-; X86-NEXT: subl %esi, %edx
+; X86-NEXT: addl %esi, %edx
; X86-NEXT: popl %esi
; X86-NEXT: .cfi_def_cfa_offset 4
; X86-NEXT: retl
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