when merging two loads, make sure to take the min of their alignment,

not the max.  This didn't matter until the previous patch because
instcombine would refuse to sink loads with differenting alignments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85738 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 4c6c2bb2ac8c41a2c72a9074a0156688dd95e846..07681d15d87634f89b1c881069ee14f5d89f0b2b 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10774,7 +10774,7 @@ Instruction *InstCombiner::FoldPHIArgLoadIntoPHI(PHINode &PN) {
     if ((LoadAlignment != 0) != (LI->getAlignment() != 0))
       return 0;
     
-    LoadAlignment = std::max(LoadAlignment, LI->getAlignment());
+    LoadAlignment = std::min(LoadAlignment, LI->getAlignment());
     
     // If the PHI is of volatile loads and the load block has multiple
     // successors, sinking it would remove a load of the volatile value from

diff --git a/test/Transforms/InstCombine/phi.ll b/test/Transforms/InstCombine/phi.ll
index 08d28b4de7ef1955a9de5e9915fd56231d3de220..d5665f6b68c3ef93834596a3cc62387195156e2d 100644 (file)
--- a/test/Transforms/InstCombine/phi.ll
+++ b/test/Transforms/InstCombine/phi.ll
@@ -157,9 +157,35 @@ bb1:
 bb2:
   %E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
   ret i32 %E
+; CHECK: @test9
 ; CHECK:       bb2:
 ; CHECK-NEXT:        phi i32* [ %B, %bb ], [ %A, %bb1 ]
 ; CHECK-NEXT:   %E = load i32* %{{[^,]*}}, align 1
 ; CHECK-NEXT:   ret i32 %E
 
 }
+
+define i32 @test10(i32* %A, i32* %B) {
+entry:
+  %c = icmp eq i32* %A, null
+  br i1 %c, label %bb1, label %bb
+
+bb:
+  %C = load i32* %B, align 16
+  br label %bb2
+
+bb1:
+  %D = load i32* %A, align 32
+  br label %bb2
+
+bb2:
+  %E = phi i32 [ %C, %bb ], [ %D, %bb1 ]
+  ret i32 %E
+; CHECK: @test10
+; CHECK:       bb2:
+; CHECK-NEXT:        phi i32* [ %B, %bb ], [ %A, %bb1 ]
+; CHECK-NEXT:   %E = load i32* %{{[^,]*}}, align 16
+; CHECK-NEXT:   ret i32 %E
+
+}
+