[X86] Disable mul -> shl + lea combine when compiling for minsize

Differential Revision: http://reviews.llvm.org/D11904 llvm-svn: 244740
llvm · Aug 12, 2015 · fe0d9bb · fe0d9bb
1 parent 94f2bb5
commit fe0d9bb
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diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -23436,6 +23436,10 @@ static SDValue PerformCMOVCombine(SDNode *N, SelectionDAG &DAG,
 /// LEA + SHL, LEA + LEA.
 static SDValue PerformMulCombine(SDNode *N, SelectionDAG &DAG,
                                  TargetLowering::DAGCombinerInfo &DCI) {
+  // An imul is usually smaller than the alternative sequence.
+  if (DAG.getMachineFunction().getFunction()->optForMinSize())
+    return SDValue();
+
   if (DCI.isBeforeLegalize() || DCI.isCalledByLegalizer())
     return SDValue();
 

diff --git a/llvm/test/CodeGen/X86/imul.ll b/llvm/test/CodeGen/X86/imul.ll
@@ -108,3 +108,21 @@ define i64 @mul40_64(i64 %A) {
     %mul = mul i64 %A, 40
     ret i64 %mul
 }
+
+define i32 @mul4_32_minsize(i32 %A) minsize {
+; X64-LABEL: mul4_32_minsize:
+; X64: leal
+; X86-LABEL: mul4_32_minsize:
+; X86: shll
+    %mul = mul i32 %A, 4
+    ret i32 %mul
+}
+
+define i32 @mul40_32_minsize(i32 %A) minsize {
+; X64-LABEL: mul40_32_minsize:
+; X64: imull
+; X86-LABEL: mul40_32_minsize:
+; X86: imull
+    %mul = mul i32 %A, 40
+    ret i32 %mul
+}