Transforms: Don't create bad branch weights when folding a switch
This avoids creating branch weight metadata of length one when we fold
cases into the default of a switch instruction, which was triggering
an assert.
llvm-svn: 196845
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 2768041..8a15c7c 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -127,8 +127,10 @@
// dest. If so, eliminate it as an explicit compare.
if (i.getCaseSuccessor() == DefaultDest) {
MDNode* MD = SI->getMetadata(LLVMContext::MD_prof);
- // MD should have 2 + NumCases operands.
- if (MD && MD->getNumOperands() == 2 + SI->getNumCases()) {
+ unsigned NCases = SI->getNumCases();
+ // Fold the case metadata into the default if there will be any branches
+ // left, unless the metadata doesn't match the switch.
+ if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
// Collect branch weights into a vector.
SmallVector<uint32_t, 8> Weights;
for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
diff --git a/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll b/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll
index 4022ed6..9125446 100644
--- a/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll
+++ b/llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll
@@ -293,6 +293,23 @@
ret void
}
+;; test12 - Don't crash if the whole switch is removed
+define void @test12(i32 %M, i32 %N) nounwind uwtable {
+entry:
+ switch i32 %N, label %sw.bb [
+ i32 1, label %sw.bb
+ ], !prof !9
+; CHECK: test12
+; CHECK-NOT: switch
+
+sw.bb:
+ call void @helper(i32 0)
+ br label %sw.epilog
+
+sw.epilog:
+ ret void
+}
+
!0 = metadata !{metadata !"branch_weights", i32 3, i32 5}
!1 = metadata !{metadata !"branch_weights", i32 1, i32 1}
!2 = metadata !{metadata !"branch_weights", i32 1, i32 2}
@@ -302,6 +319,7 @@
!6 = metadata !{metadata !"branch_weights", i32 1, i32 3}
!7 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8, i32 7}
!8 = metadata !{metadata !"branch_weights", i32 33, i32 9, i32 8}
+!9 = metadata !{metadata !"branch_weights", i32 7, i32 6}
; CHECK: !0 = metadata !{metadata !"branch_weights", i32 5, i32 11}
; CHECK: !1 = metadata !{metadata !"branch_weights", i32 1, i32 5}