JIT: Fix switch peeling flags propagation (#79748)

Otherwise we could propagate overlapping flags that change meaning.
Extracted from early liveness PR.

diff --git a/src/coreclr/jit/fgopt.cpp b/src/coreclr/jit/fgopt.cpp
index 50bc965..16eb52c 100644 (file)
--- a/src/coreclr/jit/fgopt.cpp
+++ b/src/coreclr/jit/fgopt.cpp
@@ -4321,9 +4321,9 @@ bool Compiler::fgOptimizeSwitchJumps()
 
         // Update flags
         //
-        switchTree->gtFlags = switchTree->AsOp()->gtOp1->gtFlags;
-        dominantCaseCompare->gtFlags |= dominantCaseCompare->AsOp()->gtOp1->gtFlags;
-        jmpTree->gtFlags |= dominantCaseCompare->gtFlags;
+        switchTree->gtFlags = switchTree->AsOp()->gtOp1->gtFlags & GTF_ALL_EFFECT;
+        dominantCaseCompare->gtFlags |= dominantCaseCompare->AsOp()->gtOp1->gtFlags & GTF_ALL_EFFECT;
+        jmpTree->gtFlags |= dominantCaseCompare->gtFlags & GTF_ALL_EFFECT;
         dominantCaseCompare->gtFlags |= GTF_RELOP_JMP_USED | GTF_DONT_CSE;
 
         // Wire up the new control flow.