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

Extend (truncate (load)) folding 

DAGCombiner could fold (truncate (load)) -> smaller load if the original
load was the width of the truncation result or wider.  This patch extends
it to handle cases where the original load was narrower (and so the
extension type stays the same).

llvm-svn: 197030
This commit is contained in:
Richard Sandiford 2013-12-11 11:37:27 +00:00
parent 88adc5e815
commit d1093636cc
2 changed files with 28 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -5632,6 +5632,20 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
SDValue Reduced = ReduceLoadWidth(N);
if (Reduced.getNode())
return Reduced;
// Handle the case where the load remains an extending load even
// after truncation.
if (N0.hasOneUse() && ISD::isUNINDEXEDLoad(N0.getNode())) {
LoadSDNode *LN0 = cast<LoadSDNode>(N0);
if (!LN0->isVolatile() &&
LN0->getMemoryVT().getStoreSizeInBits() < VT.getSizeInBits()) {
SDValue NewLoad = DAG.getExtLoad(LN0->getExtensionType(), SDLoc(LN0),
VT, LN0->getChain(), LN0->getBasePtr(),
LN0->getMemoryVT(),
LN0->getMemOperand());
DAG.ReplaceAllUsesOfValueWith(N0.getValue(1), NewLoad.getValue(1));
return NewLoad;
}
}
}
// fold (trunc (concat ... x ...)) -> (concat ..., (trunc x), ...)),
// where ... are all 'undef'.

14
llvm/test/CodeGen/SystemZ/insert-06.ll
View File

@ -178,3 +178,17 @@ define i64 @f14(i64 %a, i64 %b) {
%ext = sext i1 %res to i64
ret i64 %ext
}
; Check another representation of f8.
define i64 @f15(i64 %a, i8 *%src) {
; CHECK-LABEL: f15:
; CHECK-NOT: {{%r[23]}}
; CHECK: lb %r2, 0(%r3)
; CHECK: br %r14
%byte = load i8 *%src
%b = sext i8 %byte to i64
%low = and i64 %b, 4294967295
%high = and i64 %a, -4294967296
%res = or i64 %high, %low
ret i64 %res
}