Fix the folding of multiplication into addresses on x86, which was broken

by the recent {U,S}MUL_LOHI changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43230 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 853ac11..9b7808e 100644 (file)
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -681,6 +681,11 @@ bool X86DAGToDAGISel::MatchAddress(SDOperand N, X86ISelAddressMode &AM,
       }
     break;
 
+  case ISD::SMUL_LOHI:
+  case ISD::UMUL_LOHI:
+    // A mul_lohi where we need the low part can be folded as a plain multiply.
+    if (N.ResNo != 0) break;
+    // FALL THROUGH
   case ISD::MUL:
     // X*[3,5,9] -> X+X*[2,4,8]
     if (!Available &&

diff --git a/test/CodeGen/X86/fold-mul-lohi.ll b/test/CodeGen/X86/fold-mul-lohi.ll
new file mode 100644 (file)
index 0000000..abd8ddd
--- /dev/null
+++ b/test/CodeGen/X86/fold-mul-lohi.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | llc -march=x86 | not grep lea
+; RUN: llvm-as < %s | llc -march=x86-64 | not grep lea
+
+@B = external global [1000 x i8], align 32
+@A = external global [1000 x i8], align 32
+@P = external global [1000 x i8], align 32
+
+define void @foo(i32 %m) {
+entry:
+       %tmp1 = icmp sgt i32 %m, 0
+       br i1 %tmp1, label %bb, label %return
+
+bb:
+       %i.019.0 = phi i32 [ %indvar.next, %bb ], [ 0, %entry ]
+       %tmp2 = getelementptr [1000 x i8]* @B, i32 0, i32 %i.019.0
+       %tmp3 = load i8* %tmp2, align 4
+       %tmp4 = mul i8 %tmp3, 2
+       %tmp5 = getelementptr [1000 x i8]* @A, i32 0, i32 %i.019.0
+       store i8 %tmp4, i8* %tmp5, align 4
+       %tmp8 = mul i32 %i.019.0, 9
+       %tmp10 = getelementptr [1000 x i8]* @P, i32 0, i32 %tmp8
+       store i8 17, i8* %tmp10, align 4
+       %indvar.next = add i32 %i.019.0, 1
+       %exitcond = icmp eq i32 %indvar.next, %m
+       br i1 %exitcond, label %return, label %bb
+
+return:
+       ret void
+}
+