cmd/vet: teach asm checker about PEXTRD’s op size

Fixes #15271

Change-Id: I28e3fb5bde1e6fd5b263b1434873b8ce051aee97
Reviewed-on: https://go-review.googlesource.com/22083
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/vet/asmdecl.go

@@ -559,6 +559,11 @@ func asmCheckVar(badf func(string, ...interface{}), fn *asmFunc, line, expr stri
 				src = 8
 				break
 			}
+			if strings.HasPrefix(op, "P") && strings.HasSuffix(op, "RD") {
+				// PINSRD, PEXTRD, etc
+				src = 4
+				break
+			}
 			if strings.HasPrefix(op, "F") && (strings.HasSuffix(op, "F") || strings.HasSuffix(op, "FP")) {
 				// FMOVFP, FXCHF, etc
 				src = 4

src/cmd/vet/testdata/asm.go

@@ -31,3 +31,5 @@ func nosplit(x int)
 func rodata(x int)
 func noptr(x int)
 func wrapper(x int)
+
+func f15271() (x uint32)

src/cmd/vet/testdata/asm1.s

@@ -252,3 +252,14 @@ TEXT ·returnnamed(SB),0,$0-41
 
 TEXT ·returnintmissing(SB),0,$0-8
 	RET // ERROR "RET without writing to 8-byte ret\+0\(FP\)"
+
+
+// issue 15271
+TEXT ·f15271(SB), NOSPLIT, $0-4
+    // Stick 123 into the low 32 bits of X0.
+    MOVQ $123, AX
+    PINSRD $0, AX, X0
+
+    // Return them.
+    PEXTRD $0, X0, x+0(FP)
+    RET