[PowerPC] stop folding if result rlwinm mask is wrap while original rlwinm is not.

%1:g8rc = RLWINM8 %0:g8rc, 0, 16, 9
%2:g8rc = RLWINM8 killed %1:g8rc, 0, 0, 31
->
%2:g8rc = RLWINM8 %0:g8rc, 0, 16, 9

The above folding is wrong. Before transformation, %2:g8rc is 32 bit value. After
transformation, %2:g8rc becomes a 64 bit value.
This patch fixes above issue.

Reviewed by: steven.zhang

Differential Revision: https://reviews.llvm.org/D71833

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp b/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
index 0d45b0ae793..02a5cdcbcae 100644
--- a/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
+++ b/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
@@ -919,8 +919,12 @@ bool PPCMIPeephole::simplifyCode(void) {
 
           LLVM_DEBUG(dbgs() << "With: ");
           LLVM_DEBUG(MI.dump());
-        } else if (isRunOfOnes((unsigned)(FinalMask.getZExtValue()), NewMB,
-                               NewME) || SrcMaskFull) {
+        } else if ((isRunOfOnes((unsigned)(FinalMask.getZExtValue()), NewMB,
+                               NewME) && NewMB <= NewME)|| SrcMaskFull) {
+          // Here we only handle MBMI <= MEMI case, so NewMB must be no bigger
+          // than NewME. Otherwise we get a 64 bit value after folding, but MI
+          // return a 32 bit value.
+
           // If FoldingReg has only one use and it it not RLWINMo and
           // RLWINM8o, safe to delete its def SrcMI. Otherwise keep it.
           if (MRI->hasOneNonDBGUse(FoldingReg) &&