Merge r98416 from mainline.

tlattner · tlattner · commit 18d41baa161d · 2010-03-23T16:58:02.000Z
Fix a typo in ValueTracking that's causing instcombine to delete needed shift instructions.

llvm-svn: 99289
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
@@ -779,7 +779,7 @@ unsigned llvm::ComputeNumSignBits(Value *V, const TargetData *TD,
     for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
       if (Tmp == 1) return Tmp;
       Tmp = std::min(Tmp,
-                     ComputeNumSignBits(PN->getIncomingValue(1), TD, Depth+1));
+                     ComputeNumSignBits(PN->getIncomingValue(i), TD, Depth+1));
     }
     return Tmp;
   }
diff --git a/llvm/test/Transforms/InstCombine/shift-sra.ll b/llvm/test/Transforms/InstCombine/shift-sra.ll
@@ -56,3 +56,23 @@ C:
 ; CHECK: %P = phi i64
 ; CHECK-NEXT: ret i64 %P
 }
+
+; rdar://7732987
+define i32 @test5(i32 %Y) {
+  br i1 undef, label %A, label %C
+A:
+  br i1 undef, label %B, label %D
+B:
+  br label %D
+C:
+  br i1 undef, label %D, label %E
+D:
+  %P = phi i32 [0, %A], [0, %B], [%Y, %C] 
+  %S = ashr i32 %P, 16
+  ret i32 %S
+; CHECK: @test5
+; CHECK: %P = phi i32
+; CHECK-NEXT: ashr i32 %P, 16
+E:
+  ret i32 0
+}

Original file line number	Diff line number	Diff line change
`@@ -779,7 +779,7 @@ unsigned llvm::ComputeNumSignBits(Value V, const TargetData TD,`
`779`	`779`	`for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {`
`780`	`780`	`if (Tmp == 1) return Tmp;`
`781`	`781`	`Tmp = std::min(Tmp,`
`782`		`- ComputeNumSignBits(PN->getIncomingValue(1), TD, Depth+1));`
	`782`	`+ ComputeNumSignBits(PN->getIncomingValue(i), TD, Depth+1));`
`783`	`783`	`}`
`784`	`784`	`return Tmp;`
`785`	`785`	`}`