[llvm] 1b57749 - [PowerPC] stop folding if result rlwinm mask is wrap while original rlwinm is not.

[via llvm-commits]

Author: czhengsz
Date: 2019-12-25T21:56:18-05:00
New Revision: 1b57749a5334ae3d854c6f8732e741ef9f977219

URL: https://github.com/llvm/llvm-project/commit/1b57749a5334ae3d854c6f8732e741ef9f977219
DIFF: https://github.com/llvm/llvm-project/commit/1b57749a5334ae3d854c6f8732e741ef9f977219.diff

LOG: [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

Added: 
    

Modified: 
    llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
    llvm/test/CodeGen/PowerPC/fold-rlwinm.mir

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp b/llvm/lib/Target/PowerPC/PPCMIPeephole.cpp
index 0d45b0ae7937..02a5cdcbcae6 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) &&

diff  --git a/llvm/test/CodeGen/PowerPC/fold-rlwinm.mir b/llvm/test/CodeGen/PowerPC/fold-rlwinm.mir
index cf96bc116390..bc7c461d3197 100644
--- a/llvm/test/CodeGen/PowerPC/fold-rlwinm.mir
+++ b/llvm/test/CodeGen/PowerPC/fold-rlwinm.mir
@@ -77,6 +77,21 @@ body: |
     BLR8 implicit $lr8, implicit $rm
 ...
 ---
+name: testFoldRLWINMResultWrapped
+#CHECK : name : testFoldRLWINMResultWrapped
+tracksRegLiveness: true
+body: |
+  bb.0.entry:
+    liveins: $x3
+    %0:g8rc = COPY $x3
+    %1:gprc = COPY %0.sub_32:g8rc
+    %2:gprc = RLWINM %1:gprc, 10, 20, 10
+    ; CHECK: %2:gprc = RLWINM %1, 10, 20, 10
+    %3:gprc = RLWINM %2:gprc, 10, 0, 31
+    ; CHECK: %3:gprc = RLWINM %2, 10, 0, 31
+    BLR8 implicit $lr8, implicit $rm
+...
+---
 name: testFoldRLWINMMultipleUses
 #CHECK : name : testFoldRLWINMMultipleUses
 tracksRegLiveness: true