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[X86] Reduce some 32-bit imuls into lea + shl

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Reduce integer multiplication by a constant of the form k*2^c, where k is in {3,5,9} into a lea + shl. Previously it was only done for imulq on 64-bit platforms, but it makes sense for imull and 32-bit as well.

Differential Revision: http://reviews.llvm.org/D7196

llvm-svn: 227308
This commit is contained in:
Michael Kuperstein 2015-01-28 14:08:22 +00:00
parent 31413a17ef
commit 139e0bbb66
4 changed files with 115 additions and 29 deletions
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5
lib/Target/X86/X86ISelLowering.cpp
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@ -1721,8 +1721,7 @@ void X86TargetLowering::resetOperationActions() {
setTargetDAGCombine(ISD::SETCC);
setTargetDAGCombine(ISD::INTRINSIC_WO_CHAIN);
setTargetDAGCombine(ISD::BUILD_VECTOR);
if (Subtarget->is64Bit())
setTargetDAGCombine(ISD::MUL);
setTargetDAGCombine(ISD::MUL);
setTargetDAGCombine(ISD::XOR);
computeRegisterProperties();
@ -24046,7 +24045,7 @@ static SDValue PerformMulCombine(SDNode *N, SelectionDAG &DAG,
return SDValue();
EVT VT = N->getValueType(0);
if (VT != MVT::i64)
if (VT != MVT::i64 && VT != MVT::i32)
return SDValue();
ConstantSDNode *C = dyn_cast<ConstantSDNode>(N->getOperand(1));

110
test/CodeGen/X86/imul.ll Normal file
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@ -0,0 +1,110 @@
; RUN: llc < %s -mtriple=x86_64-pc-linux-gnu | FileCheck %s --check-prefix=X64
; RUN: llc < %s -mtriple=x86_64-pc-linux-gnux32 | FileCheck %s --check-prefix=X64
; RUN: llc < %s -mtriple=i686-pc-linux | FileCheck %s --check-prefix=X86
define i32 @mul4_32(i32 %A) {
; X64-LABEL: mul4_32:
; X64: leal
; X86-LABEL: mul4_32:
; X86: shll
%mul = mul i32 %A, 4
ret i32 %mul
}
define i64 @mul4_64(i64 %A) {
; X64-LABEL: mul4_64:
; X64: leaq
; X86-LABEL: mul4_64:
; X86: shldl
; X86: shll
%mul = mul i64 %A, 4
ret i64 %mul
}
define i32 @mul4096_32(i32 %A) {
; X64-LABEL: mul4096_32:
; X64: shll
; X86-LABEL: mul4096_32:
; X86: shll
%mul = mul i32 %A, 4096
ret i32 %mul
}
define i64 @mul4096_64(i64 %A) {
; X64-LABEL: mul4096_64:
; X64: shlq
; X86-LABEL: mul4096_64:
; X86: shldl
; X86: shll
%mul = mul i64 %A, 4096
ret i64 %mul
}
define i32 @mulmin4096_32(i32 %A) {
; X64-LABEL: mulmin4096_32:
; X64: shll
; X64-NEXT: negl
; X86-LABEL: mulmin4096_32:
; X86: shll
; X86-NEXT: negl
%mul = mul i32 %A, -4096
ret i32 %mul
}
define i64 @mulmin4096_64(i64 %A) {
; X64-LABEL: mulmin4096_64:
; X64: shlq
; X64-NEXT: negq
; X86-LABEL: mulmin4096_64:
; X86: shldl
; X86-NEXT: shll
; X86-NEXT: xorl
; X86-NEXT: negl
; X86-NEXT: sbbl
%mul = mul i64 %A, -4096
ret i64 %mul
}
define i32 @mul3_32(i32 %A) {
; X64-LABEL: mul3_32:
; X64: leal
; X86-LABEL: mul3_32:
; But why?!
; X86: imull
%mul = mul i32 %A, 3
ret i32 %mul
}
define i64 @mul3_64(i64 %A) {
; X64-LABEL: mul3_64:
; X64: leaq
; X86-LABEL: mul3_64:
; X86: mull
; X86-NEXT: imull
%mul = mul i64 %A, 3
ret i64 %mul
}
define i32 @mul40_32(i32 %A) {
; X64-LABEL: mul40_32:
; X64: shll
; X64-NEXT: leal
; X86-LABEL: mul40_32:
; X86: shll
; X86-NEXT: leal
%mul = mul i32 %A, 40
ret i32 %mul
}
define i64 @mul40_64(i64 %A) {
; X64-LABEL: mul40_64:
; X64: shlq
; X64-NEXT: leaq
; X86-LABEL: mul40_64:
; X86: leal
; X86-NEXT: movl
; X86-NEXT: mull
; X86-NEXT: leal
%mul = mul i64 %A, 40
ret i64 %mul
}

25
test/CodeGen/X86/imul64-lea.ll
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@ -1,25 +0,0 @@
; RUN: llc < %s -mtriple=x86_64-pc-linux-gnu | FileCheck %s
; RUN: llc < %s -mtriple=x86_64-pc-linux-gnux32 | FileCheck %s
; Test that 64-bit LEAs are generated for both LP64 and ILP32 in 64-bit mode.
declare i64 @foo64()
define i64 @test64() {
%tmp.0 = tail call i64 @foo64( )
%tmp.1 = mul i64 %tmp.0, 9
; CHECK-NOT: mul
; CHECK: leaq
ret i64 %tmp.1
}
; Test that 32-bit LEAs are generated for both LP64 and ILP32 in 64-bit mode.
declare i32 @foo32()
define i32 @test32() {
%tmp.0 = tail call i32 @foo32( )
%tmp.1 = mul i32 %tmp.0, 9
; CHECK-NOT: mul
; CHECK: leal
ret i32 %tmp.1
}

4
test/Transforms/LoopStrengthReduce/X86/ivchain-X86.ll
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@ -59,7 +59,9 @@ exit:
;
; X32: @user
; expensive address computation in the preheader
; X32: imul
; X32: shll $4
; X32: lea
; X32: lea
; X32: %loop
; complex address modes
; X32: (%{{[^)]+}},%{{[^)]+}},