[llvm-commits] [llvm] r50859 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll

[Chris Lattner]

Author: lattner
Date: Thu May  8 12:20:30 2008
New Revision: 50859

URL: http://llvm.org/viewvc/llvm-project?rev=50859&view=rev
Log:
Make instcombine's DSE respect loads as well as stores.  It is not safe to
delete the first store in:

store x -> p
load p
store y -> p

This is for PR2297.


Added:
    llvm/trunk/test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=50859&r1=50858&r2=50859&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Thu May  8 12:20:30 2008
@@ -10426,7 +10426,7 @@
     }
     
     // Don't skip over loads or things that can modify memory.
-    if (BBI->mayWriteToMemory())
+    if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory())
       break;
   }
   

Added: llvm/trunk/test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll?rev=50859&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/2008-05-08-LiveStoreDelete.ll Thu May  8 12:20:30 2008
@@ -0,0 +1,25 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {store i8} | count 3
+; PR2297
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin8"
+
+define i32 @a() nounwind  {
+entry:
+	%"alloca point" = bitcast i32 0 to i32		; <i32> [#uses=0]
+	%tmp1 = call i8* @malloc( i32 10 ) nounwind 		; <i8*> [#uses=5]
+	%tmp3 = getelementptr i8* %tmp1, i32 1		; <i8*> [#uses=1]
+	store i8 0, i8* %tmp3, align 1
+	%tmp5 = getelementptr i8* %tmp1, i32 0		; <i8*> [#uses=1]
+	store i8 1, i8* %tmp5, align 1
+	%tmp7 = call i32 @strlen( i8* %tmp1 ) nounwind readonly 		; <i32> [#uses=1]
+	%tmp9 = getelementptr i8* %tmp1, i32 0		; <i8*> [#uses=1]
+	store i8 0, i8* %tmp9, align 1
+	%tmp11 = call i32 (...)* @b( i8* %tmp1 ) nounwind 		; <i32> [#uses=0]
+	ret i32 %tmp7
+}
+
+declare i8* @malloc(i32) nounwind 
+
+declare i32 @strlen(i8*) nounwind readonly 
+
+declare i32 @b(...)