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cmd/internal/obj/ppc64: remove C_UCON optab matching class

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This optab matching rule was used to match signed 16 bit values shifted
left by 16 bits. Unsigned 16 bit values greater than 0x7FFF<<16 were
classified as C_U32CON which led to larger than necessary codegen.

Instead, rewrite logical/arithmetic operations in the preprocessor pass
to use the 16 bit shifted immediate operation (e.g ADDIS vs ADD). This
simplifies the optab matching rules, while also minimizing codegen size
for large unsigned values.

Note, ADDIS sign-extends the constant argument, all others do not.

For matching opcodes, this means:
	MOVD $is<<16,Rx becomes ADDIS $is,Rx or ORIS $is,Rx
	MOVW $is<<16,Rx becomes ADDIS $is,Rx
	ADD $is<<16,[Rx,]Ry becomes ADDIS $is[Rx,]Ry
	OR $is<<16,[Rx,]Ry becomes ORIS $is[Rx,]Ry
	XOR $is<<16,[Rx,]Ry becomes XORIS $is[Rx,]Ry

Change-Id: I1a988d9f52517a04bb8dc2e41d7caf3d5fff867c
Reviewed-on: https://go-review.googlesource.com/c/go/+/536735
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
This commit is contained in:
Paul E. Murphy 2023-10-12 09:25:30 -05:00 • committed by Paul Murphy
parent 6b818b08f9
commit 3128aeec87
7 changed files with 84 additions and 83 deletions
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4
test/codegen/mathbits.go
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@ -340,8 +340,8 @@ func TrailingZeros16(n uint16) int {
// arm:"ORR\t\\$65536","CLZ",-"MOVHU\tR"
// arm64:"ORR\t\\$65536","RBITW","CLZW",-"MOVHU\tR",-"RBIT\t",-"CLZ\t"
// s390x:"FLOGR","OR\t\\$65536"
// ppc64x/power8:"POPCNTD","OR\\t\\$65536"
// ppc64x/power9:"CNTTZD","OR\\t\\$65536"
// ppc64x/power8:"POPCNTD","ORIS\\t\\$1"
// ppc64x/power9:"CNTTZD","ORIS\\t\\$1"
// wasm:"I64Ctz"
return bits.TrailingZeros16(n)
}