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

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227308 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86ISelLowering.cpp

@@ -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));

test/CodeGen/X86/imul.ll

@@ -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
+}

test/CodeGen/X86/imul64-lea.ll

@@ -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
-}
-

test/Transforms/LoopStrengthReduce/X86/ivchain-X86.ll

@@ -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: (%{{[^)]+}},%{{[^)]+}},