[llvm-commits] [llvm] r115205 - in /llvm/trunk: lib/Transforms/Scalar/GVN.cpp test/Transforms/GVN/load-pre-licm.ll

[Owen Anderson]

Author: resistor
Date: Thu Sep 30 15:53:04 2010
New Revision: 115205

URL: http://llvm.org/viewvc/llvm-project?rev=115205&view=rev
Log:
We do want to allow LoadPRE to perform LICM-like transformations: we already consider PHI nodes to be negligible for
code size (making this transform code size neutral), and it allows us to hoist values out of loops, which is always
a good thing.

Added:
    llvm/trunk/test/Transforms/GVN/load-pre-licm.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/GVN.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=115205&r1=115204&r2=115205&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Thu Sep 30 15:53:04 2010
@@ -1545,19 +1545,6 @@
   assert(TmpBB);
   LoadBB = TmpBB;
 
-  // If we have a repl set with LI itself in it, this means we have a loop where
-  // at least one of the values is LI.  Since this means that we won't be able
-  // to eliminate LI even if we insert uses in the other predecessors, we will
-  // end up increasing code size.  Reject this by scanning for LI.
-  for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
-    if (ValuesPerBlock[i].isSimpleValue() &&
-        ValuesPerBlock[i].getSimpleValue() == LI) {
-      // Skip cases where LI is the only definition, even for EnableFullLoadPRE.
-      if (!EnableFullLoadPRE || e == 1)
-        return false;
-    }
-  }
-
   // FIXME: It is extremely unclear what this loop is doing, other than
   // artificially restricting loadpre.
   if (isSinglePred) {

Added: llvm/trunk/test/Transforms/GVN/load-pre-licm.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVN/load-pre-licm.ll?rev=115205&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/GVN/load-pre-licm.ll (added)
+++ llvm/trunk/test/Transforms/GVN/load-pre-licm.ll Thu Sep 30 15:53:04 2010
@@ -0,0 +1,39 @@
+; RUN: opt -S -gvn < %s | FileCheck %s
+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-n8:16:32"
+target triple = "i386-apple-darwin11.0.0"
+
+ at sortlist = external global [5001 x i32], align 4
+
+define void @Bubble() nounwind noinline {
+; CHECK: entry:
+; CHECK-NEXT: %tmp7.pre = load i32
+entry:
+  br label %while.body5
+
+; CHECK: while.body5:
+; CHECK: %tmp7 = phi i32
+; CHECK-NOT: %tmp7 = load i32
+while.body5:
+  %indvar = phi i32 [ 0, %entry ], [ %tmp6, %if.end ]
+  %tmp5 = add i32 %indvar, 2
+  %arrayidx9 = getelementptr [5001 x i32]* @sortlist, i32 0, i32 %tmp5
+  %tmp6 = add i32 %indvar, 1
+  %arrayidx = getelementptr [5001 x i32]* @sortlist, i32 0, i32 %tmp6
+  %tmp7 = load i32* %arrayidx, align 4
+  %tmp10 = load i32* %arrayidx9, align 4
+  %cmp11 = icmp sgt i32 %tmp7, %tmp10
+  br i1 %cmp11, label %if.then, label %if.end
+
+; CHECK: if.then:
+if.then:
+  store i32 %tmp10, i32* %arrayidx, align 4
+  store i32 %tmp7, i32* %arrayidx9, align 4
+  br label %if.end
+
+if.end:
+  %exitcond = icmp eq i32 %tmp6, 100
+  br i1 %exitcond, label %while.end.loopexit, label %while.body5
+
+while.end.loopexit:
+  ret void
+}