When doing address-mode sinking, expand the base register first, rather

than the scaled register. This makes it more likely that subsequent
AddrModeMatcher queries will match the new address the same way as the
old, instead of accidentally matching what had been the base register
as the new scaled register, and then failing to match the scaled register.
This fixes some problems with address-mode sinking multiple muls into a
block, which will be a lot more common with some upcoming
LoopStrengthReduction changes.

llvm-svn: 93935

1 files changed, 17 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 9c1b440bd5c..c3139a511bb 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -617,7 +617,23 @@ bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
           TLI->getTargetData()->getIntPtrType(AccessTy->getContext());
 
     Value *Result = 0;
-    // Start with the scale value.
+
+    // Start with the base register. Do this first so that subsequent address
+    // matching finds it last, which will prevent it from trying to match it
+    // as the scaled value in case it happens to be a mul. That would be
+    // problematic if we've sunk a different mul for the scale, because then
+    // we'd end up sinking both muls.
+    if (AddrMode.BaseReg) {
+      Value *V = AddrMode.BaseReg;
+      if (isa<PointerType>(V->getType()))
+        V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
+      if (V->getType() != IntPtrTy)
+        V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true,
+                                        "sunkaddr", InsertPt);
+      Result = V;
+    }
+
+    // Add the scale value.
     if (AddrMode.Scale) {
       Value *V = AddrMode.ScaledReg;
       if (V->getType() == IntPtrTy) {
@@ -634,17 +650,6 @@ bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
         V = BinaryOperator::CreateMul(V, ConstantInt::get(IntPtrTy,
                                                                 AddrMode.Scale),
                                       "sunkaddr", InsertPt);
-      Result = V;
-    }
-
-    // Add in the base register.
-    if (AddrMode.BaseReg) {
-      Value *V = AddrMode.BaseReg;
-      if (isa<PointerType>(V->getType()))
-        V = new PtrToIntInst(V, IntPtrTy, "sunkaddr", InsertPt);
-      if (V->getType() != IntPtrTy)
-        V = CastInst::CreateIntegerCast(V, IntPtrTy, /*isSigned=*/true,
-                                        "sunkaddr", InsertPt);
       if (Result)
         Result = BinaryOperator::CreateAdd(Result, V, "sunkaddr", InsertPt);
       else