[LLVMbugs] [Bug 711] NEW: Coallescing physregs with virtregs should allow spilling the virtreg portion
bugzilla-daemon at cs.uiuc.edu
bugzilla-daemon at cs.uiuc.edu
Wed Feb 22 23:50:35 PST 2006
http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=711
Summary: Coallescing physregs with virtregs should allow spilling
the virtreg portion
Product: libraries
Version: 1.0
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: Common Code Generator Code
AssignedTo: unassignedbugs at nondot.org
ReportedBy: sabre at nondot.org
This problem is causing fastcc on x86 to fail in some corner cases. Here's a testcase:
---
target endian = little
target pointersize = 32
target triple = "i686-pc-linux-gnu"
%.str_28 = external global [24 x sbyte] ; <[24 x sbyte]*> [#uses=1]
implementation ; Functions:
fastcc void %apply_stencil_op_to_pixels(int* %tmp.414, uint %n,
int* %x, int* %y, uint %oper, ubyte* %mask) {
entry:
switch uint %oper, label %label.5 [
uint 5386, label %label.6
]
label.5: ; preds = %entry
br label %no_exit.8
no_exit.8: ; preds = %then.17, %label.5
%tmp.409 = getelementptr ubyte* %mask, uint 0 ; <ubyte*> [#uses=1]
%tmp.410 = load ubyte* %tmp.409 ; <ubyte> [#uses=0]
br label %then.17
then.17: ; preds = %no_exit.8
%tmp.415 = load int* %tmp.414
%tmp.417 = load ubyte** null ; <ubyte*> [#uses=1]
%tmp.425 = getelementptr int* %y, uint 0 ; <int*> [#uses=1]
%tmp.426 = load int* %tmp.425 ; <int> [#uses=1]
%tmp.437 = getelementptr ubyte* %tmp.417, int %tmp.426
; <ubyte*> [#uses=2]
%tmp.440 = load ubyte* %tmp.437 ; <ubyte> [#uses=1]
store ubyte %tmp.440, ubyte* %tmp.437
%tmp.405101 = setlt uint 0, %n ; <bool> [#uses=1]
br bool %tmp.405101, label %no_exit.8, label %UnifiedReturnBlock
label.6: ; preds = %entry
%tmp.4.i = tail call uint %fwrite( sbyte* getelementptr ([24 x sbyte]* %.str_28, int 0, int 0), uint 23,
uint 1, sbyte* null ) ; <uint> [#uses=0]
ret void
UnifiedReturnBlock: ; preds = %then.17, %no_exit.8
ret void
}
declare int %fprintf(%struct._IO_FILE*, sbyte*, ...)
declare uint %fwrite(sbyte*, uint, uint, sbyte*)
---
Compiled with 'llc -enable-x86-fastcc', this crashes llc.
This is due to the coallescer coallescing virtregs with both EAX and EDX, which makes them unavailable
to satisfy spills, causing the RA to run out of registers. We want to coallesce physregs when possible,
but we cannot pin them in the spiller: we have to be able to uncoallesce them.
This is almost certainly related to Bug 699.
-Chris
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