[SimplifyCFG] Update (AND) IR flags when CSE'ing instructions

We were updating metadata but not IR flags. Because we pick an arbitrary instruction to be the CSE candidate, it comes down to luck (50% or less chance) if this results in broken codegen or not, which is why PR30373 which is actually not the fault of the commit it was bisected down to.

Fixes PR30373.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281889 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 877e55928d4454a41c049c921ca9e76274725a26..90ce672018292e9493031a584eff829bcc45f0ab 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1527,10 +1527,12 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
     I0->getOperandUse(O).set(NewOperands[O]);
   I0->moveBefore(&*BBEnd->getFirstInsertionPt());
 
-  // Update metadata.
+  // Update metadata and IR flags.
   for (auto *I : Insts)
-    if (I != I0)
+    if (I != I0) {
       combineMetadataForCSE(I0, I);
+      I0->andIRFlags(I);
+    }
 
   if (!isa<StoreInst>(I0)) {
     // canSinkLastInstruction checked that all instructions were used by

diff --git a/test/Transforms/SimplifyCFG/sink-common-code.ll b/test/Transforms/SimplifyCFG/sink-common-code.ll
index e944a9bc1e9c773dba46796a26b1676d65a29914..54f87052c7aecbb16fb44bd5599b7b9271e9a098 100644 (file)
--- a/test/Transforms/SimplifyCFG/sink-common-code.ll
+++ b/test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -699,6 +699,62 @@ if.end:
 ; CHECK: store
 ; CHECK: store
 
+define i32 @test_pr30373a(i1 zeroext %flag, i32 %x, i32 %y) {
+entry:
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  %x0 = call i32 @foo(i32 %x, i32 0) nounwind readnone
+  %y0 = call i32 @foo(i32 %x, i32 1) nounwind readnone
+  %z0 = lshr i32 %y0, 8
+  br label %if.end
+
+if.else:
+  %x1 = call i32 @foo(i32 %y, i32 0) nounwind readnone
+  %y1 = call i32 @foo(i32 %y, i32 1) nounwind readnone
+  %z1 = lshr exact i32 %y1, 8
+  br label %if.end
+
+if.end:
+  %xx = phi i32 [ %x0, %if.then ], [ %x1, %if.else ]
+  %yy = phi i32 [ %z0, %if.then ], [ %z1, %if.else ]
+  %ret = add i32 %xx, %yy
+  ret i32 %ret
+}
+
+; CHECK-LABEL: test_pr30373a
+; CHECK: lshr
+; CHECK-NOT: exact
+; CHECK: }
+
+define i32 @test_pr30373b(i1 zeroext %flag, i32 %x, i32 %y) {
+entry:
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  %x0 = call i32 @foo(i32 %x, i32 0) nounwind readnone
+  %y0 = call i32 @foo(i32 %x, i32 1) nounwind readnone
+  %z0 = lshr exact i32 %y0, 8
+  br label %if.end
+
+if.else:
+  %x1 = call i32 @foo(i32 %y, i32 0) nounwind readnone
+  %y1 = call i32 @foo(i32 %y, i32 1) nounwind readnone
+  %z1 = lshr i32 %y1, 8
+  br label %if.end
+
+if.end:
+  %xx = phi i32 [ %x0, %if.then ], [ %x1, %if.else ]
+  %yy = phi i32 [ %z0, %if.then ], [ %z1, %if.else ]
+  %ret = add i32 %xx, %yy
+  ret i32 %ret
+}
+
+; CHECK-LABEL: test_pr30373b
+; CHECK: lshr
+; CHECK-NOT: exact
+; CHECK: }
+
 ; CHECK: !0 = !{!1, !1, i64 0}
 ; CHECK: !1 = !{!"float", !2}
 ; CHECK: !2 = !{!"an example type tree"}