================
@@ -3158,6 +3172,166 @@ bool
SPIRVInstructionSelector::selectFirstBitHigh(Register ResVReg,
}
}
+bool SPIRVInstructionSelector::selectFirstBitLow16(Register ResVReg,
+ const SPIRVType *ResType,
+ MachineInstr &I) const {
+ // OpUConvert treats the operand bits as an unsigned i16 and zero extends it
+ // to an unsigned i32. As this leaves all the least significant bits
unchanged
+ // the first set bit from the LSB side doesn't change.
+ Register ExtReg = MRI->createVirtualRegister(GR.getRegClass(ResType));
+ bool Result = selectNAryOpWithSrcs(
+ ExtReg, ResType, I, {I.getOperand(2).getReg()}, SPIRV::OpUConvert);
+ return Result && selectFirstBitLow32(ResVReg, ResType, I, ExtReg);
+}
+
+bool SPIRVInstructionSelector::selectFirstBitLow32(Register ResVReg,
+ const SPIRVType *ResType,
+ MachineInstr &I,
+ Register SrcReg) const {
+ return BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(SPIRV::OpExtInst))
+ .addDef(ResVReg)
+ .addUse(GR.getSPIRVTypeID(ResType))
+ .addImm(static_cast<uint32_t>(SPIRV::InstructionSet::GLSL_std_450))
+ .addImm(GL::FindILsb)
+ .addUse(SrcReg)
+ .constrainAllUses(TII, TRI, RBI);
+}
+
+bool SPIRVInstructionSelector::selectFirstBitLow64(Register ResVReg,
+ const SPIRVType *ResType,
+ MachineInstr &I) const {
+ Register OpReg = I.getOperand(2).getReg();
+
+ // 1. Split int64 into 2 pieces using a bitcast
+ unsigned ComponentCount = GR.getScalarOrVectorComponentCount(ResType);
+ SPIRVType *BaseType = GR.retrieveScalarOrVectorIntType(ResType);
+ MachineIRBuilder MIRBuilder(I);
+ SPIRVType *PostCastType =
+ GR.getOrCreateSPIRVVectorType(BaseType, 2 * ComponentCount, MIRBuilder);
+ Register BitcastReg =
+ MRI->createVirtualRegister(GR.getRegClass(PostCastType));
+ bool Result =
+ selectUnOpWithSrc(BitcastReg, PostCastType, I, OpReg, SPIRV::OpBitcast);
+
+ // 2. Find the first set bit from the LSB side for all the pieces in #1
+ Register FBLReg = MRI->createVirtualRegister(GR.getRegClass(PostCastType));
+ Result = Result && selectFirstBitLow32(FBLReg, PostCastType, I, BitcastReg);
+
+ // 3. Split result vector into high bits and low bits
----------------
s-perron wrote:
All of step 3 is the same as the `selectFirstBitHigh64`, right? Could that be
moved into a separate function?
https://github.com/llvm/llvm-project/pull/116858
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
