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Arm64: Optimize pairs of "str wzr" to "str xzr" #84350

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Merged
kunalspathak merged 1 commit into from
Apr 6, 2023
Merged

Arm64: Optimize pairs of "str wzr" to "str xzr" #84350

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10 changes: 10 additions & 0 deletions src/coreclr/jit/emitarm64.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16220,6 +16220,16 @@ bool emitter::ReplaceLdrStrWithPairInstr(
// Remove the last instruction written.
emitRemoveLastInstruction();

// Combine two 32 bit stores of value zero into one 64 bit store
if (ins == INS_str && reg1 == REG_ZR && oldReg1 == REG_ZR && size == EA_4BYTE)
{

// The first register is at the lower offset for the ascending order
ssize_t offset = (optimizationOrder == eRO_ascending ? oldImm : imm) * size;
emitIns_R_R_I(INS_str, EA_8BYTE, REG_ZR, reg2, offset, INS_OPTS_NONE);
return true;
}

// Emit the new instruction. Make sure to scale the immediate value by the operand size.
if (optimizationOrder == eRO_ascending)
{
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