[llvm] afe9264 - Revert "[CaptureTracking] Avoid overly restrictive dominates check"

[Anna Thomas via llvm-commits]

Author: Anna Thomas
Date: 2020-11-05T12:27:15-05:00
New Revision: afe92642cc73db48ea46a1dc1a534492249040a7

URL: https://github.com/llvm/llvm-project/commit/afe92642cc73db48ea46a1dc1a534492249040a7
DIFF: https://github.com/llvm/llvm-project/commit/afe92642cc73db48ea46a1dc1a534492249040a7.diff

LOG: Revert "[CaptureTracking] Avoid overly restrictive dominates check"

This reverts commit 15694fd6ad955c6a16b446a6324364111a49ae8b.
Need to investigate and fix a failing clang test: synchronized.m.
Might need a test update.

Added: 
    

Modified: 
    llvm/lib/Analysis/CaptureTracking.cpp
    llvm/test/Transforms/MemCpyOpt/callslot.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/CaptureTracking.cpp b/llvm/lib/Analysis/CaptureTracking.cpp
index 15e022c64402..06a3b81e0362 100644
--- a/llvm/lib/Analysis/CaptureTracking.cpp
+++ b/llvm/lib/Analysis/CaptureTracking.cpp
@@ -133,10 +133,10 @@ namespace {
         return !isPotentiallyReachableFromMany(Worklist, BB, nullptr, DT);
       }
 
-      // If the value is defined in a 
diff erent basic block than BeforeHere,
-      // there is no need to explore the use if there is no path from I to
-      // BeforeHere.
-      if (BeforeHere != I &&
+      // If the value is defined in the same basic block as use and BeforeHere,
+      // there is no need to explore the use if BeforeHere dominates use.
+      // Check whether there is a path from I to BeforeHere.
+      if (BeforeHere != I && DT->dominates(BeforeHere, I) &&
           !isPotentiallyReachable(I, BeforeHere, nullptr, DT))
         return true;
 

diff  --git a/llvm/test/Transforms/MemCpyOpt/callslot.ll b/llvm/test/Transforms/MemCpyOpt/callslot.ll
index c9d23644cf51..f85a67667950 100644
--- a/llvm/test/Transforms/MemCpyOpt/callslot.ll
+++ b/llvm/test/Transforms/MemCpyOpt/callslot.ll
@@ -186,39 +186,6 @@ define void @capture_before_call_argmemonly() {
   ret void
 }
 
-; There is no path from the capture back to the memcpy.
-; So we can perform the call slot optimization.
-define void @capture_nopath_call_argmemonly(i1 %cond) {
-; CHECK-LABEL: @capture_nopath_call_argmemonly(
-; CHECK-NEXT:    [[DEST:%.*]] = alloca [16 x i8], align 1
-; CHECK-NEXT:    [[SRC:%.*]] = alloca [16 x i8], align 1
-; CHECK-NEXT:    [[DEST_I8:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
-; CHECK-NEXT:    [[SRC_I8:%.*]] = bitcast [16 x i8]* [[SRC]] to i8*
-; CHECK-NEXT:    br i1 [[COND:%.*]], label [[CAPTURES:%.*]], label [[NOCAPTURES:%.*]]
-; CHECK:       captures:
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST_I8]])
-; CHECK-NEXT:    ret void
-; CHECK:       nocaptures:
-; CHECK-NEXT:    [[DEST1:%.*]] = bitcast [16 x i8]* [[DEST]] to i8*
-; CHECK-NEXT:    call void @accept_ptr(i8* [[DEST1]]) [[ATTR5:#.*]]
-; CHECK-NEXT:    ret void
-;
-  %dest = alloca [16 x i8]
-  %src = alloca [16 x i8]
-  %dest.i8 = bitcast [16 x i8]* %dest to i8*
-  %src.i8 = bitcast [16 x i8]* %src to i8*
-  br i1 %cond, label %captures, label %nocaptures
-
-captures:
-  call void @accept_ptr(i8* %dest.i8) ; capture
-  ret void
-
-nocaptures:
-  call void @accept_ptr(i8* %src.i8) argmemonly nounwind
-  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dest.i8, i8* %src.i8, i64 16, i1 false)
-  ret void
-}
-
 define void @capture_before_call_argmemonly_nounwind() {
 ; CHECK-LABEL: @capture_before_call_argmemonly_nounwind(
 ; CHECK-NEXT:    [[DEST:%.*]] = alloca [16 x i8], align 1