[llvm-commits] [llvm] r44044 - in /llvm/trunk: lib/Transforms/Scalar/SimplifyCFG.cpp test/Transforms/SimplifyCFG/iterative-simplify.ll
Chris Lattner
sabre at nondot.org
Mon Nov 12 23:32:39 PST 2007
Author: lattner
Date: Tue Nov 13 01:32:38 2007
New Revision: 44044
URL: http://llvm.org/viewvc/llvm-project?rev=44044&view=rev
Log:
Implement PR1786 by iterating between dead cycle elimination
and simplifycfg in the rare cases when it is needed.
Added:
llvm/trunk/test/Transforms/SimplifyCFG/iterative-simplify.ll
Modified:
llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp?rev=44044&r1=44043&r2=44044&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SimplifyCFG.cpp Tue Nov 13 01:32:38 2007
@@ -27,6 +27,7 @@
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Pass.h"
+#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
@@ -50,9 +51,9 @@
}
static bool MarkAliveBlocks(BasicBlock *BB,
- SmallPtrSet<BasicBlock*, 16> &Reachable) {
+ SmallPtrSet<BasicBlock*, 128> &Reachable) {
- std::vector<BasicBlock*> Worklist;
+ SmallVector<BasicBlock*, 128> Worklist;
Worklist.push_back(BB);
bool Changed = false;
while (!Worklist.empty()) {
@@ -93,42 +94,46 @@
return Changed;
}
-
-// It is possible that we may require multiple passes over the code to fully
-// simplify the CFG.
-//
-bool CFGSimplifyPass::runOnFunction(Function &F) {
- SmallPtrSet<BasicBlock*, 16> Reachable;
+/// RemoveUnreachableBlocks - Remove blocks that are not reachable, even if they
+/// are in a dead cycle. Return true if a change was made, false otherwise.
+static bool RemoveUnreachableBlocks(Function &F) {
+ SmallPtrSet<BasicBlock*, 128> Reachable;
bool Changed = MarkAliveBlocks(F.begin(), Reachable);
-
+
// If there are unreachable blocks in the CFG...
- if (Reachable.size() != F.size()) {
- assert(Reachable.size() < F.size());
- NumSimpl += F.size()-Reachable.size();
-
- // Loop over all of the basic blocks that are not reachable, dropping all of
- // their internal references...
- for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB)
- if (!Reachable.count(BB)) {
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI!=SE; ++SI)
- if (Reachable.count(*SI))
- (*SI)->removePredecessor(BB);
- BB->dropAllReferences();
- }
-
- for (Function::iterator I = ++F.begin(); I != F.end();)
- if (!Reachable.count(I))
- I = F.getBasicBlockList().erase(I);
- else
- ++I;
-
- Changed = true;
- }
+ if (Reachable.size() == F.size())
+ return Changed;
+
+ assert(Reachable.size() < F.size());
+ NumSimpl += F.size()-Reachable.size();
+
+ // Loop over all of the basic blocks that are not reachable, dropping all of
+ // their internal references...
+ for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB)
+ if (!Reachable.count(BB)) {
+ for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI!=SE; ++SI)
+ if (Reachable.count(*SI))
+ (*SI)->removePredecessor(BB);
+ BB->dropAllReferences();
+ }
+
+ for (Function::iterator I = ++F.begin(); I != F.end();)
+ if (!Reachable.count(I))
+ I = F.getBasicBlockList().erase(I);
+ else
+ ++I;
+
+ return true;
+}
+/// IterativeSimplifyCFG - Call SimplifyCFG on all the blocks in the function,
+/// iterating until no more changes are made.
+static bool IterativeSimplifyCFG(Function &F) {
+ bool Changed = false;
bool LocalChange = true;
while (LocalChange) {
LocalChange = false;
-
+
// Loop over all of the basic blocks (except the first one) and remove them
// if they are unneeded...
//
@@ -140,6 +145,31 @@
}
Changed |= LocalChange;
}
-
return Changed;
}
+
+// It is possible that we may require multiple passes over the code to fully
+// simplify the CFG.
+//
+bool CFGSimplifyPass::runOnFunction(Function &F) {
+ bool EverChanged = RemoveUnreachableBlocks(F);
+ EverChanged |= IterativeSimplifyCFG(F);
+
+ // If neither pass changed anything, we're done.
+ if (!EverChanged) return false;
+
+ // IterativeSimplifyCFG can (rarely) make some loops dead. If this happens,
+ // RemoveUnreachableBlocks is needed to nuke them, which means we should
+ // iterate between the two optimizations. We structure the code like this to
+ // avoid reruning IterativeSimplifyCFG if the second pass of
+ // RemoveUnreachableBlocks doesn't do anything.
+ if (!RemoveUnreachableBlocks(F))
+ return true;
+
+ do {
+ EverChanged = IterativeSimplifyCFG(F);
+ EverChanged |= RemoveUnreachableBlocks(F);
+ } while (EverChanged);
+
+ return true;
+}
Added: llvm/trunk/test/Transforms/SimplifyCFG/iterative-simplify.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/iterative-simplify.ll?rev=44044&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/iterative-simplify.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/iterative-simplify.ll Tue Nov 13 01:32:38 2007
@@ -0,0 +1,100 @@
+; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | not grep bb17
+; PR1786
+
+define i32 @main() {
+entry:
+ %retval = alloca i32, align 4 ; <i32*> [#uses=1]
+ %i = alloca i32, align 4 ; <i32*> [#uses=7]
+ %z = alloca i32, align 4 ; <i32*> [#uses=4]
+ %z16 = alloca i32, align 4 ; <i32*> [#uses=4]
+ %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
+ store i32 0, i32* %i
+ %toBool = icmp ne i8 1, 0 ; <i1> [#uses=1]
+ br i1 %toBool, label %cond_true, label %cond_false
+
+cond_true: ; preds = %entry
+ store i32 0, i32* %z
+ br label %bb
+
+bb: ; preds = %cond_next, %cond_true
+ %tmp = load i32* %z ; <i32> [#uses=1]
+ %tmp1 = sub i32 %tmp, 16384 ; <i32> [#uses=1]
+ store i32 %tmp1, i32* %z
+ %tmp2 = load i32* %i ; <i32> [#uses=1]
+ %tmp3 = add i32 %tmp2, 1 ; <i32> [#uses=1]
+ store i32 %tmp3, i32* %i
+ %tmp4 = load i32* %i ; <i32> [#uses=1]
+ %tmp5 = icmp sgt i32 %tmp4, 262144 ; <i1> [#uses=1]
+ %tmp56 = zext i1 %tmp5 to i8 ; <i8> [#uses=1]
+ %toBool7 = icmp ne i8 %tmp56, 0 ; <i1> [#uses=1]
+ br i1 %toBool7, label %cond_true8, label %cond_next
+
+cond_true8: ; preds = %bb
+ call void @abort( )
+ unreachable
+
+cond_next: ; preds = %bb
+ %tmp9 = load i32* %z ; <i32> [#uses=1]
+ %tmp10 = icmp ne i32 %tmp9, 0 ; <i1> [#uses=1]
+ %tmp1011 = zext i1 %tmp10 to i8 ; <i8> [#uses=1]
+ %toBool12 = icmp ne i8 %tmp1011, 0 ; <i1> [#uses=1]
+ br i1 %toBool12, label %bb, label %bb13
+
+bb13: ; preds = %cond_next
+ call void @exit( i32 0 )
+ unreachable
+
+cond_false: ; preds = %entry
+ %toBool14 = icmp ne i8 1, 0 ; <i1> [#uses=1]
+ br i1 %toBool14, label %cond_true15, label %cond_false33
+
+cond_true15: ; preds = %cond_false
+ store i32 0, i32* %z16
+ br label %bb17
+
+bb17: ; preds = %cond_next27, %cond_true15
+ %tmp18 = load i32* %z16 ; <i32> [#uses=1]
+ %tmp19 = sub i32 %tmp18, 16384 ; <i32> [#uses=1]
+ store i32 %tmp19, i32* %z16
+ %tmp20 = load i32* %i ; <i32> [#uses=1]
+ %tmp21 = add i32 %tmp20, 1 ; <i32> [#uses=1]
+ store i32 %tmp21, i32* %i
+ %tmp22 = load i32* %i ; <i32> [#uses=1]
+ %tmp23 = icmp sgt i32 %tmp22, 262144 ; <i1> [#uses=1]
+ %tmp2324 = zext i1 %tmp23 to i8 ; <i8> [#uses=1]
+ %toBool25 = icmp ne i8 %tmp2324, 0 ; <i1> [#uses=1]
+ br i1 %toBool25, label %cond_true26, label %cond_next27
+
+cond_true26: ; preds = %bb17
+ call void @abort( )
+ unreachable
+
+cond_next27: ; preds = %bb17
+ %tmp28 = load i32* %z16 ; <i32> [#uses=1]
+ %tmp29 = icmp ne i32 %tmp28, 0 ; <i1> [#uses=1]
+ %tmp2930 = zext i1 %tmp29 to i8 ; <i8> [#uses=1]
+ %toBool31 = icmp ne i8 %tmp2930, 0 ; <i1> [#uses=1]
+ br i1 %toBool31, label %bb17, label %bb32
+
+bb32: ; preds = %cond_next27
+ call void @exit( i32 0 )
+ unreachable
+
+cond_false33: ; preds = %cond_false
+ call void @exit( i32 0 )
+ unreachable
+
+cond_next34: ; No predecessors!
+ br label %cond_next35
+
+cond_next35: ; preds = %cond_next34
+ br label %return
+
+return: ; preds = %cond_next35
+ %retval36 = load i32* %retval ; <i32> [#uses=1]
+ ret i32 %retval36
+}
+
+declare void @abort()
+
+declare void @exit(i32)
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