maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Some reassociate optimizations create new instructions, which they insert just 

before the expression root.  Any existing operators that are changed to use one
of them needs to be moved between it and the expression root, and recursively
for the operators using that one.  When I rewrote RewriteExprTree I accidentally
inverted the logic, resulting in the compacting going down from operators to
operands rather than up from operands to the operators using them, oops.  Fix
this, resolving PR12963.

llvm-svn: 159265
This commit is contained in:
Duncan Sands 2012-06-27 14:19:00 +00:00
parent d326a6cf93
commit 514db117bd
2 changed files with 21 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
llvm/lib/Transforms/Scalar/Reassociate.cpp
View File

@ -673,16 +673,10 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
// original in some non-trivial way, requiring the clearing of optional flags.
// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
BinaryOperator *ExpressionChanged = 0;
BinaryOperator *Previous;
BinaryOperator *Op = 0;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
for (unsigned i = 0; ; ++i) {
assert(!NodesToRewrite.empty() &&
"Optimized expressions has more nodes than original!");
Previous = Op; Op = NodesToRewrite.pop_back_val();
if (ExpressionChanged)
// Compactify the tree instructions together with each other to guarantee
// that the expression tree is dominated by all of Ops.
Op->moveBefore(Previous);
BinaryOperator *Op = NodesToRewrite.pop_back_val();
// The last operation (which comes earliest in the IR) is special as both
// operands will come from Ops, rather than just one with the other being
@ -771,15 +765,17 @@ void Reassociate::RewriteExprTree(BinaryOperator *I,
}
// If the expression changed non-trivially then clear out all subclass data
// starting from the operator specified in ExpressionChanged.
if (ExpressionChanged) {
// starting from the operator specified in ExpressionChanged, and compactify
// the operators to just before the expression root to guarantee that the
// expression tree is dominated by all of Ops.
if (ExpressionChanged)
do {
ExpressionChanged->clearSubclassOptionalData();
if (ExpressionChanged == I)
break;
ExpressionChanged->moveBefore(I);
ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->use_begin());
} while (1);
}
// Throw away any left over nodes from the original expression.
for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)

14
llvm/test/Transforms/Reassociate/crash.ll
View File

@ -119,3 +119,17 @@ for.cond: ; preds = %for.cond, %entry
%conv = zext i16 %p to i32
br label %for.cond
}
; PR12963
@a = external global i8
define i8 @f0(i8 %x) {
%t0 = load i8* @a
%t1 = mul i8 %x, %x
%t2 = mul i8 %t1, %t1
%t3 = mul i8 %t2, %t2
%t4 = mul i8 %t3, %x
%t5 = mul i8 %t4, %t4
%t6 = mul i8 %t5, %x
%t7 = mul i8 %t6, %t0
ret i8 %t7
}