[llvm-commits] [llvm] r152635 - in /llvm/trunk: include/llvm/Analysis/Loads.h lib/Analysis/Loads.cpp lib/Transforms/Scalar/JumpThreading.cpp test/Transforms/JumpThreading/thread-loads.ll
Chris Lattner
sabre at nondot.org
Tue Mar 13 11:07:41 PDT 2012
Author: lattner
Date: Tue Mar 13 13:07:41 2012
New Revision: 152635
URL: http://llvm.org/viewvc/llvm-project?rev=152635&view=rev
Log:
enhance jump threading to preserve TBAA information when PRE'ing loads,
fixing rdar://11039258, an issue that came up when inspecting clang's
bootstrapped codegen.
Modified:
llvm/trunk/include/llvm/Analysis/Loads.h
llvm/trunk/lib/Analysis/Loads.cpp
llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
llvm/trunk/test/Transforms/JumpThreading/thread-loads.ll
Modified: llvm/trunk/include/llvm/Analysis/Loads.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Loads.h?rev=152635&r1=152634&r2=152635&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/Loads.h (original)
+++ llvm/trunk/include/llvm/Analysis/Loads.h Tue Mar 13 13:07:41 2012
@@ -20,6 +20,7 @@
class AliasAnalysis;
class TargetData;
+class MDNode;
/// isSafeToLoadUnconditionally - Return true if we know that executing a load
/// from this value cannot trap. If it is not obviously safe to load from the
@@ -41,10 +42,15 @@
/// MaxInstsToScan specifies the maximum instructions to scan in the block.
/// If it is set to 0, it will scan the whole block. You can also optionally
/// specify an alias analysis implementation, which makes this more precise.
+///
+/// If TBAATag is non-null and a load or store is found, the TBAA tag from the
+/// load or store is recorded there. If there is no TBAA tag or if no access
+/// is found, it is left unmodified.
Value *FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan = 6,
- AliasAnalysis *AA = 0);
+ AliasAnalysis *AA = 0,
+ MDNode **TBAATag = 0);
}
Modified: llvm/trunk/lib/Analysis/Loads.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Loads.cpp?rev=152635&r1=152634&r2=152635&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/Loads.cpp (original)
+++ llvm/trunk/lib/Analysis/Loads.cpp Tue Mar 13 13:07:41 2012
@@ -17,6 +17,7 @@
#include "llvm/GlobalAlias.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IntrinsicInst.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Operator.h"
using namespace llvm;
@@ -160,10 +161,15 @@
/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
/// it is set to 0, it will scan the whole block. You can also optionally
/// specify an alias analysis implementation, which makes this more precise.
+///
+/// If TBAATag is non-null and a load or store is found, the TBAA tag from the
+/// load or store is recorded there. If there is no TBAA tag or if no access
+/// is found, it is left unmodified.
Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
BasicBlock::iterator &ScanFrom,
unsigned MaxInstsToScan,
- AliasAnalysis *AA) {
+ AliasAnalysis *AA,
+ MDNode **TBAATag) {
if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
// If we're using alias analysis to disambiguate get the size of *Ptr.
@@ -191,15 +197,19 @@
// (This is true even if the load is volatile or atomic, although
// those cases are unlikely.)
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
+ if (AreEquivalentAddressValues(LI->getOperand(0), Ptr)) {
+ if (TBAATag) *TBAATag = LI->getMetadata(LLVMContext::MD_tbaa);
return LI;
+ }
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
// If this is a store through Ptr, the value is available!
// (This is true even if the store is volatile or atomic, although
// those cases are unlikely.)
- if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
+ if (AreEquivalentAddressValues(SI->getOperand(1), Ptr)) {
+ if (TBAATag) *TBAATag = SI->getMetadata(LLVMContext::MD_tbaa);
return SI->getOperand(0);
+ }
// If Ptr is an alloca and this is a store to a different alloca, ignore
// the store. This is a trivial form of alias analysis that is important
Modified: llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp?rev=152635&r1=152634&r2=152635&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/JumpThreading.cpp Tue Mar 13 13:07:41 2012
@@ -857,6 +857,9 @@
if (BBIt != LoadBB->begin())
return false;
+ // If all of the loads and stores that feed the value have the same TBAA tag,
+ // then we can propagate it onto any newly inserted loads.
+ MDNode *TBAATag = LI->getMetadata(LLVMContext::MD_tbaa);
SmallPtrSet<BasicBlock*, 8> PredsScanned;
typedef SmallVector<std::pair<BasicBlock*, Value*>, 8> AvailablePredsTy;
@@ -875,11 +878,16 @@
// Scan the predecessor to see if the value is available in the pred.
BBIt = PredBB->end();
- Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6);
+ MDNode *ThisTBAATag = 0;
+ Value *PredAvailable = FindAvailableLoadedValue(LoadedPtr, PredBB, BBIt, 6,
+ 0, &ThisTBAATag);
if (!PredAvailable) {
OneUnavailablePred = PredBB;
continue;
}
+
+ // If tbaa tags disagree or are not present, forget about them.
+ if (TBAATag != ThisTBAATag) TBAATag = 0;
// If so, this load is partially redundant. Remember this info so that we
// can create a PHI node.
@@ -939,6 +947,9 @@
LI->getAlignment(),
UnavailablePred->getTerminator());
NewVal->setDebugLoc(LI->getDebugLoc());
+ if (TBAATag)
+ NewVal->setMetadata(LLVMContext::MD_tbaa, TBAATag);
+
AvailablePreds.push_back(std::make_pair(UnavailablePred, NewVal));
}
Modified: llvm/trunk/test/Transforms/JumpThreading/thread-loads.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/JumpThreading/thread-loads.ll?rev=152635&r1=152634&r2=152635&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/JumpThreading/thread-loads.ll (original)
+++ llvm/trunk/test/Transforms/JumpThreading/thread-loads.ll Tue Mar 13 13:07:41 2012
@@ -1,12 +1,12 @@
; RUN: opt < %s -jump-threading -S | FileCheck %s
-; rdar://6402033
-; Test that we can thread through the block with the partially redundant load (%2).
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-darwin7"
-define i32 @foo(i32* %P) nounwind {
-; CHECK: foo
+; Test that we can thread through the block with the partially redundant load (%2).
+; rdar://6402033
+define i32 @test1(i32* %P) nounwind {
+; CHECK: @test1
entry:
%0 = tail call i32 (...)* @f1() nounwind ; <i32> [#uses=1]
%1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
@@ -39,3 +39,43 @@
declare i32 @f1(...)
declare i32 @f2(...)
+
+
+;; Check that we preserve TBAA information.
+; rdar://11039258
+
+define i32 @test2(i32* %P) nounwind {
+; CHECK: @test2
+entry:
+ %0 = tail call i32 (...)* @f1() nounwind ; <i32> [#uses=1]
+ %1 = icmp eq i32 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %bb1, label %bb
+
+bb: ; preds = %entry
+; CHECK: bb1.thread:
+; CHECK: store{{.*}}, !tbaa !0
+; CHECK: br label %bb3
+ store i32 42, i32* %P, align 4, !tbaa !0
+ br label %bb1
+
+bb1: ; preds = %entry, %bb
+ %res.0 = phi i32 [ 1, %bb ], [ 0, %entry ]
+ %2 = load i32* %P, align 4, !tbaa !0
+ %3 = icmp sgt i32 %2, 36
+ br i1 %3, label %bb3, label %bb2
+
+bb2: ; preds = %bb1
+ %4 = tail call i32 (...)* @f2() nounwind
+ ret i32 %res.0
+
+bb3: ; preds = %bb1
+; CHECK: bb3:
+; CHECK: %res.01 = phi i32 [ 1, %bb1.thread ], [ 0, %bb1 ]
+; CHECK: ret i32 %res.01
+ ret i32 %res.0
+}
+
+!0 = metadata !{metadata !"int", metadata !1}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA", null}
+
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