[llvm-commits] [llvm] r85738 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/phi.ll

[Chris Lattner]

Author: lattner
Date: Sun Nov  1 14:07:07 2009
New Revision: 85738

URL: http://llvm.org/viewvc/llvm-project?rev=85738&view=rev
Log:
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.

Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/phi.ll

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=85738&r1=85737&r2=85738&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Nov  1 14:07:07 2009
@@ -10774,7 +10774,7 @@
     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

Modified: llvm/trunk/test/Transforms/InstCombine/phi.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/phi.ll?rev=85738&r1=85737&r2=85738&view=diff

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/phi.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/phi.ll Sun Nov  1 14:07:07 2009
@@ -157,9 +157,35 @@
 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
+
+}
+