[go/dev.simd] [dev.simd] cmd/internal/obj/arm64: add indexed element operand patterns for VFMLA/VFMLS/VFMUL

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Jonathan Swinney (Gerrit)

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Mar 27, 2026, 4:32:43 PM (12 days ago) Mar 27
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[dev.simd] cmd/internal/obj/arm64: add indexed element operand patterns for VFMLA/VFMLS/VFMUL

Add C_ELEM optab entries for indexed element forms of VFMLA, VFMLS,
and VFMUL, supporting both scalar and vector variants:

  VFMLA V6.S[0], F2, F14          // scalar indexed
  VFMLA V28.S[2], V2.S2, V30.S2   // vector indexed

Two new optab entries using AVFMLA as root opcode (covering AVFMLS
and AVFMUL via oprangeset):
  {AVFMLA, C_ELEM, C_FREG, C_NONE, C_FREG, ...}  // scalar
  {AVFMLA, C_ELEM, C_ARNG, C_NONE, C_ARNG, ...}  // vector

New encoding case 111 implements the ARM encoding:
  Scalar: 0x5f800000 | sz<<22 | L<<21 | M<<20 | Rm<<16 | op<<12 | H<<11 | Rn<<5 | Rd
  Vector: 0x0f800000 | Q<<30 | sz<<22 | L<<21 | M<<20 | Rm<<16 | op<<12 | H<<11 | Rn<<5 | Rd

For .S: sz=0, H=index[1], L=index[0], M=Vm[4]
For .D: sz=1, H=index[0], L=0, M=Vm[4]

Encodings verified against GNU as output.

Uncomment the 6 corresponding encoding tests in arm64enc.s.
Change-Id: Iab5218f34e8bc3c306bd7a720b7bea818f4f23db

Change diff

diff --git a/src/cmd/asm/internal/asm/testdata/arm64enc.s b/src/cmd/asm/internal/asm/testdata/arm64enc.s
index 0876080..24f2c2d 100644
--- a/src/cmd/asm/internal/asm/testdata/arm64enc.s
+++ b/src/cmd/asm/internal/asm/testdata/arm64enc.s
@@ -576,11 +576,11 @@
 	VFMINP V10.S2, F20                         // 54f9b07e
 	VFMINP V1.D2, V10.D2, V3.D2               // 43f5e16e
 	VFMINV V11.S4, F9                          // 69f9b06e
-	//TODO VFMLA V6.S[0], F2, F14              // 4e10865f
-	//TODO VFMLA V28.S[2], V2.S2, V30.S2       // 5e189c0f
+	VFMLA V6.S[0], F2, F14                     // 4e10865f
+	VFMLA V28.S[2], V2.S2, V30.S2              // 5e189c0f
 	VFMLA V29.S2, V20.S2, V14.S2               // 8ece3d0e
-	//TODO VFMLS V24.D[1], F3, F17             // 7158d85f
-	//TODO VFMLS V10.S[0], V11.S2, V10.S2      // 6a518a0f
+	VFMLS V24.D[1], F3, F17                    // 7158d85f
+	VFMLS V10.S[0], V11.S2, V10.S2             // 6a518a0f
 	VFMLS V29.S2, V27.S2, V17.S2               // 71cfbd0e
 	//TODO FMOVS $(-1.625), F13                // 0d503f1e
 	//TODO FMOVD $12.5, F30                    // 1e30651e
@@ -594,8 +594,8 @@
 	//TODO VFMOV $3.125, V8.D2                 // 28f5006f
 	FMSUBS F13, F21, F13, F19                  // b3d50d1f
 	FMSUBD F11, F7, F15, F31                   // ff9d4b1f
-	//TODO VFMUL V9.S[2], F21, F19             // b39a895f
-	//TODO VFMUL V26.S[2], V26.S2, V2.S2       // 429b9a0f
+	VFMUL V9.S[2], F21, F19                    // b39a895f
+	VFMUL V26.S[2], V26.S2, V2.S2              // 429b9a0f
 	VFMUL V21.D2, V17.D2, V25.D2              // 39de756e
 	FMULS F0, F6, F24                          // d808201e
 	FMULD F5, F29, F9                          // a90b651e
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index 4dc93bd..d034b42 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -391,10 +391,16 @@
 	{AVADDV, C_ARNG, C_NONE, C_NONE, C_FREG, C_NONE, 85, 4, 0, 0, 0},
 
 	/* scalar pairwise reductions: vfaddp/vfmaxp/vfminp/vfmaxnmp/vfminnmp Vn.<T>, Fd
-	   These use AVFMLA as the root opcode so they are included in the AVFMLA oprange,
-	   which covers AVFADDP, AVFMAXP, AVFMINP, AVFMAXNMP, AVFMINNMP via oprangeset. */
+	   Use AVFMLA as the root opcode so buildop includes these in the AVFMLA oprange,
+	   which is shared with AVFADDP, AVFMAXP, AVFMINP, AVFMAXNMP, AVFMINNMP via oprangeset. */
 	{AVFMLA, C_ARNG, C_NONE, C_NONE, C_FREG, C_NONE, 110, 4, 0, 0, 0},
 
+	/* indexed element forms: vfmla/vfmls/vfmul Vm.<T>[index], Rn, Rd
+	   Use AVFMLA as the root opcode so buildop includes these in the AVFMLA oprange,
+	   which is shared with AVFMLS and AVFMUL via oprangeset. */
+	{AVFMLA, C_ELEM, C_FREG, C_NONE, C_FREG, C_NONE, 111, 4, 0, 0, 0},
+	{AVFMLA, C_ELEM, C_ARNG, C_NONE, C_ARNG, C_NONE, 111, 4, 0, 0, 0},
+
 	/* logical operations */
 	{AAND, C_ZREG, C_ZREG, C_NONE, C_ZREG, C_NONE, 1, 4, 0, 0, 0},
 	{AAND, C_ZREG, C_NONE, C_NONE, C_ZREG, C_NONE, 1, 4, 0, 0, 0},
@@ -6060,23 +6066,81 @@
 		switch p.As {
 		case AVFADDP:
 			opcode = 0x0d
-		case AVFMAXP, AVFMAXNMP:
+		case AVFMAXP:
 			opcode = 0x0f
-			if p.As == AVFMAXNMP {
-				opcode = 0x0c
-			}
-		case AVFMINP, AVFMINNMP:
+		case AVFMAXNMP:
+			opcode = 0x0c
+		case AVFMINP:
 			sz |= 2 // set sz[1] for min variants
 			opcode = 0x0f
-			if p.As == AVFMINNMP {
-				opcode = 0x0c
-			}
+		case AVFMINNMP:
+			sz |= 2 // set sz[1] for min variants
+			opcode = 0x0c
 		default:
 			c.ctxt.Diag("unsupported op %v\n", p.As)
 		}
 		rn := uint32(p.From.Reg & 31)
 		rd := uint32(p.To.Reg & 31)
 		o1 = 0x7e300800 | sz<<22 | opcode<<12 | rn<<5 | rd
+
+	case 111: /* indexed element: vfmla/vfmls/vfmul Vm.<T>[index], Rn, Rd */
+		// AdvSIMD scalar x indexed element (C_FREG dest):
+		//   0 1 0 1 1 1 1 1 1 sz L M Rm opcode H 0 Rn Rd  (base: 0x5f800000)
+		// AdvSIMD vector x indexed element (C_ARNG dest):
+		//   0 Q 0 0 1 1 1 1 1 sz L M Rm opcode H 0 Rn Rd  (base: 0x0f800000)
+		// For .S type: sz=0, L=index[0], M=Vm[4], Rm[3:0]=Vm[3:0], H=index[1]
+		// For .D type: sz=1, L=0, M=Vm[4], Rm[3:0]=Vm[3:0], H=index
+		af := int((p.From.Reg >> 5) & 15) // arrangement of C_ELEM (ARNG_S or ARNG_D)
+		index := int(p.From.Index)
+		rm := int(p.From.Reg & 31)
+		rn := uint32(p.Reg & 31)
+		rd := uint32(p.To.Reg & 31)
+		var sz, H, L, M uint32
+		switch af {
+		case ARNG_S:
+			sz = 0
+			H = uint32(index>>1) & 1
+			L = uint32(index) & 1
+			M = uint32(rm>>4) & 1
+		case ARNG_D:
+			sz = 1
+			H = uint32(index) & 1
+			L = 0
+			M = uint32(rm>>4) & 1
+		default:
+			c.ctxt.Diag("invalid arrangement: %v\n", p)
+		}
+		var opcode uint32
+		switch p.As {
+		case AVFMLA:
+			opcode = 0x1
+		case AVFMLS:
+			opcode = 0x5
+		case AVFMUL:
+			opcode = 0x9
+		default:
+			c.ctxt.Diag("unsupported op %v\n", p.As)
+		}
+		rmLow := uint32(rm) & 0xf
+		if p.To.Reg >= REG_F0 && p.To.Reg <= REG_F31 {
+			// scalar indexed element
+			o1 = 0x5f800000 | sz<<22 | L<<21 | M<<20 | rmLow<<16 | opcode<<12 | H<<11 | rn<<5 | rd
+		} else {
+			// vector indexed element: Q from destination arrangement
+			at := int((p.To.Reg >> 5) & 15)
+			var Q uint32
+			switch at {
+			case ARNG_2S:
+				Q = 0
+			case ARNG_4S:
+				Q = 1
+			case ARNG_2D:
+				Q = 1
+			default:
+				c.ctxt.Diag("invalid arrangement: %v\n", p)
+			}
+			o1 = 0x0f800000 | Q<<30 | sz<<22 | L<<21 | M<<20 | rmLow<<16 | opcode<<12 | H<<11 | rn<<5 | rd
+		}
 	}
 	out[0] = o1
 	out[1] = o2

Change information

Files:
  • M src/cmd/asm/internal/asm/testdata/arm64enc.s
  • M src/cmd/internal/obj/arm64/asm7.go
Change size: M
Delta: 2 files changed, 80 insertions(+), 16 deletions(-)
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Jonathan Swinney (Gerrit)

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Mar 27, 2026, 5:12:37 PM (12 days ago) Mar 27
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