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| author | Evan Cheng <evan.cheng@apple.com> | 2008-12-19 20:58:01 +0000 |
|---|---|---|
| committer | Evan Cheng <evan.cheng@apple.com> | 2008-12-19 20:58:01 +0000 |
| commit | 0869f78555d7799c2e3cb35d2fcffa22cbaff08f (patch) | |
| tree | f48394a78b8769c7d5cfb1fbde4c709c9734b74d /llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp | |
| parent | 091134785df8f7298d826d48f921f624612d1ab1 (diff) | |
Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this.
172 %ECX<def> = MOV32rr %reg1039<kill>
180 INLINEASM <es:subl $5,$1
sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, %EAX<kill>,
36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0
188 %EAX<def> = MOV32rr %EAX<kill>
196 %ECX<def> = MOV32rr %ECX<kill>
204 %ECX<def> = MOV32rr %ECX<kill>
212 %EAX<def> = MOV32rr %EAX<kill>
220 %EAX<def> = MOV32rr %EAX
228 %reg1039<def> = MOV32rr %ECX<kill>
The early clobber operand ties ECX input to the ECX def.
The live interval of ECX is represented as this:
%reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47)
The right way to represent this is something like
%reg20,inf = [46,47:2)[174,182:1)[181:230:0) 0@174-(182) 1@181-230 @2@46-(47)
Of course that won't work since that means overlapping live ranges defined by two val#.
The workaround for now is to add a bit to val# which says the val# is redefined by a early clobber def somewhere. This prevents the move at 228 from being optimized away by SimpleRegisterCoalescing::AdjustCopiesBackFrom.
llvm-svn: 61259
Diffstat (limited to 'llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp index 41022a6e269a..cfac82613ff8 100644 --- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp +++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp @@ -119,6 +119,26 @@ bool SimpleRegisterCoalescing::AdjustCopiesBackFrom(LiveInterval &IntA, if (ALR == IntA.end()) // Should never happen! return false; VNInfo *AValNo = ALR->valno; + // If it's re-defined by an early clobber somewhere in the live range, then + // it's not safe to eliminate the copy. FIXME: This is a temporary workaround. + // See PR3149: + // 172 %ECX<def> = MOV32rr %reg1039<kill> + // 180 INLINEASM <es:subl $5,$1 + // sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, %EAX<kill>, + // 36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0 + // 188 %EAX<def> = MOV32rr %EAX<kill> + // 196 %ECX<def> = MOV32rr %ECX<kill> + // 204 %ECX<def> = MOV32rr %ECX<kill> + // 212 %EAX<def> = MOV32rr %EAX<kill> + // 220 %EAX<def> = MOV32rr %EAX + // 228 %reg1039<def> = MOV32rr %ECX<kill> + // The early clobber operand ties ECX input to the ECX def. + // + // The live interval of ECX is represented as this: + // %reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47) + // The coalescer has no idea there was a def in the middle of [174,230]. + if (AValNo->redefByEC) + return false; // If AValNo is defined as a copy from IntB, we can potentially process this. // Get the instruction that defines this value number. |