[llvm] r292197 - [InstCombine] Don't DSE across readnone functions that may throw

[Sanjoy Das via llvm-commits]

Author: sanjoy
Date: Mon Jan 16 23:45:09 2017
New Revision: 292197

URL: http://llvm.org/viewvc/llvm-project?rev=292197&view=rev
Log:
[InstCombine] Don't DSE across readnone functions that may throw

Summary: Depends on D28740

Reviewers: dberlin, chandlerc, hfinkel, majnemer

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D28742

Added:
    llvm/trunk/test/Transforms/InstCombine/readnone-maythrow.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp?rev=292197&r1=292196&r2=292197&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp Mon Jan 16 23:45:09 2017
@@ -1267,8 +1267,8 @@ Instruction *InstCombiner::visitStoreIns
       break;
     }
 
-    // Don't skip over loads or things that can modify memory.
-    if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory())
+    // Don't skip over loads, throws or things that can modify memory.
+    if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory() || BBI->mayThrow())
       break;
   }
 
@@ -1391,8 +1391,8 @@ bool InstCombiner::SimplifyStoreAtEndOfB
       }
       // If we find something that may be using or overwriting the stored
       // value, or if we run out of instructions, we can't do the xform.
-      if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() ||
-          BBI == OtherBB->begin())
+      if (BBI->mayReadFromMemory() || BBI->mayThrow() ||
+          BBI->mayWriteToMemory() || BBI == OtherBB->begin())
         return false;
     }
 
@@ -1401,7 +1401,7 @@ bool InstCombiner::SimplifyStoreAtEndOfB
     // StoreBB.
     for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
       // FIXME: This should really be AA driven.
-      if (I->mayReadFromMemory() || I->mayWriteToMemory())
+      if (I->mayReadFromMemory() || I->mayThrow() || I->mayWriteToMemory())
         return false;
     }
   }

Added: llvm/trunk/test/Transforms/InstCombine/readnone-maythrow.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/readnone-maythrow.ll?rev=292197&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/readnone-maythrow.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/readnone-maythrow.ll Mon Jan 16 23:45:09 2017
@@ -0,0 +1,34 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+declare void @readnone_but_may_throw() readnone
+
+define void @f_0(i32* %ptr) {
+; CHECK-LABEL: @f_0(
+entry:
+; CHECK:  store i32 10, i32* %ptr
+; CHECK-NEXT:  call void @readnone_but_may_throw()
+; CHECK-NEXT:  store i32 20, i32* %ptr, align 4
+; CHECK:  ret void
+
+  store i32 10, i32* %ptr
+  call void @readnone_but_may_throw()
+  store i32 20, i32* %ptr
+  ret void
+}
+
+define void @f_1(i1 %cond, i32* %ptr) {
+; CHECK-LABEL: @f_1(
+; CHECK:  store i32 10, i32* %ptr
+; CHECK-NEXT:  call void @readnone_but_may_throw()
+
+  store i32 10, i32* %ptr
+  call void @readnone_but_may_throw()
+  br i1 %cond, label %left, label %merge
+
+left:
+  store i32 20, i32* %ptr
+  br label %merge
+
+merge:
+  ret void
+}