From fa3966881f7f0317803b09161602c9c7eeb2d3a3 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 26 Nov 2009 17:00:01 +0000
Subject: [PATCH] teach GetLinearExpression to be a bit more aggressive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89955 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/BasicAliasAnalysis.cpp | 11 ++++++++++-
 test/Analysis/BasicAA/gep-alias.ll  | 15 +++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index c038b207058..e10e1f2d4ce 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -400,7 +400,16 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
         V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
         Offset += RHSC->getValue();
         return V;
-      // TODO: SHL, MUL.
+      case Instruction::Mul:
+        V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
+        Offset *= RHSC->getValue();
+        Scale *= RHSC->getValue();
+        return V;
+      case Instruction::Shl:
+        V = GetLinearExpression(BOp->getOperand(0), Scale, Offset, TD);
+        Offset <<= RHSC->getValue().getLimitedValue();
+        Scale <<= RHSC->getValue().getLimitedValue();
+        return V;
       }
     }
   }
diff --git a/test/Analysis/BasicAA/gep-alias.ll b/test/Analysis/BasicAA/gep-alias.ll
index 320c9907d53..68722fbfd0e 100644
--- a/test/Analysis/BasicAA/gep-alias.ll
+++ b/test/Analysis/BasicAA/gep-alias.ll
@@ -101,3 +101,18 @@ define i32 @test6(i32* %p, i64 %i1) {
 ; CHECK: ret i32 0
 }
 
+; P[1] != P[i*4]
+define i32 @test7(i32* %p, i64 %i) {
+  %pi = getelementptr i32* %p, i64 1
+  %i.next = shl i64 %i, 2
+  %pi.next = getelementptr i32* %p, i64 %i.next
+  %x = load i32* %pi
+  store i32 42, i32* %pi.next
+  %y = load i32* %pi
+  %z = sub i32 %x, %y
+  ret i32 %z
+; CHECK: @test7
+; CHECK: ret i32 0
+}
+
+