From d8d0b6a42c09f1c5b00a4e7029b08074a3da5acd Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 19 Jan 2010 22:45:06 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93935 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/CodeGenPrepare.cpp | 29 ++++++++++++++----------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 9c1b440bd5c..c3139a511bb 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/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