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Remove <undef> from rematerialized full register 

When coalescing a small register into a subregister of a larger register,
if the larger register is rematerialized, the function updateRegDefUses
can add an <undef> flag to the rematerialized definition (since it's
treating it as only definining the coalesced subregister). While with that
assumption doing so is not incorrect, make sure to remove the flag later
on after the call to updateRegDefUses.

llvm-svn: 334845
This commit is contained in:
Krzysztof Parzyszek 2018-06-15 16:58:22 +00:00
parent 6f406d4f02
commit 1a70426ac1
2 changed files with 42 additions and 0 deletions
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5
llvm/lib/CodeGen/RegisterCoalescer.cpp
View File

@ -1231,6 +1231,11 @@ bool RegisterCoalescer::reMaterializeTrivialDef(const CoalescerPair &CP,
// Update machine operands and add flags. // Update machine operands and add flags.
updateRegDefsUses(DstReg, DstReg, DstIdx); updateRegDefsUses(DstReg, DstReg, DstIdx);
NewMI.getOperand(0).setSubReg(NewIdx); NewMI.getOperand(0).setSubReg(NewIdx);
// updateRegDefUses can add an "undef" flag to the definition, since
// it will replace DstReg with DstReg.DstIdx. If NewIdx is 0, make
// sure that "undef" is not set.
if (NewIdx == 0)
NewMI.getOperand(0).setIsUndef(false);
// Add dead subregister definitions if we are defining the whole register // Add dead subregister definitions if we are defining the whole register
// but only part of it is live. // but only part of it is live.
// This could happen if the rematerialization instruction is rematerializing // This could happen if the rematerialization instruction is rematerializing

37
llvm/test/CodeGen/Hexagon/regalloc-coal-fullreg-undef.mir Normal file
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@ -0,0 +1,37 @@
# RUN: llc -march=hexagon -run-pass=simple-register-coalescing -o - %s | FileCheck %s
# Make sure that the coalescer does not create a full definition with
# an undef flag on the destination. This used to happen when rematerializing
# a double register and coalescing a smaller reg into a subreg of it.
# CHECK-NOT: undef %[0-9]+:doubleregs = A2_tfrpi 1
---
name: fred
tracksRegLiveness: true
body: |
bb.0:
successors: %bb.1(0x80000000); %bb.1(200.00%)
%18:doubleregs = A2_tfrpi 1
%23:intregs = IMPLICIT_DEF
%24:doubleregs = IMPLICIT_DEF
bb.1:
successors: %bb.1(0x80000000); %bb.1(200.00%)
%1:doubleregs = COPY %24:doubleregs
%0:intregs = COPY %23:intregs
%13:intregs = COPY %18.isub_lo:doubleregs
%13:intregs = S2_asl_i_r_or %13:intregs, %0:intregs, 1
%15:intregs = S2_extractu %0:intregs, 1, 31
undef %17.isub_lo:doubleregs = COPY %13:intregs
%17.isub_hi:doubleregs = COPY %15:intregs
%2:doubleregs = A2_addp %17:doubleregs, %1:doubleregs
%3:intregs = A2_addi %0:intregs, -1
%23:intregs = COPY %3:intregs
%24:doubleregs = COPY %2:doubleregs
J2_jump %bb.1, implicit-def dead $pc
...