[llvm] AMDGPU: Fix instruction size for madmk/madak (PR #194361)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/194361

This caused the revert of #191461

>From 07292111626470dbae2f0705443c27e7ddb65ae2 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Mon, 27 Apr 2026 11:05:13 +0100
Subject: [PATCH] AMDGPU: Fix instruction size for madmk/madak

This caused the revert of #191461
---
 llvm/lib/Target/AMDGPU/VOP2Instructions.td    |  8 ++---
 .../AMDGPU/madmk-madak-encoding-size.ll       | 34 +++++++++++++++++++
 2 files changed, 38 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/CodeGen/AMDGPU/madmk-madak-encoding-size.ll

diff --git a/llvm/lib/Target/AMDGPU/VOP2Instructions.td b/llvm/lib/Target/AMDGPU/VOP2Instructions.td
index deb531ae180d2..d02af2addab16 100644
--- a/llvm/lib/Target/AMDGPU/VOP2Instructions.td
+++ b/llvm/lib/Target/AMDGPU/VOP2Instructions.td
@@ -865,7 +865,7 @@ defm V_CNDMASK_B16_t16 : VOP2eInst <"v_cndmask_b16_t16", VOP2e_I16_I16_I16_I1_tr
 let SubtargetPredicate = isGFX11Plus, True16Predicate = UseFakeTrue16Insts in
 defm V_CNDMASK_B16_fake16 : VOP2eInst <"v_cndmask_b16_fake16", VOP2e_I16_I16_I16_I1_fake16>;
 defm V_CNDMASK_B32 : VOP2eInst_VOPD <"v_cndmask_b32", VOP2e_I32_I32_I32_I1, 0x9, "v_cndmask_b32">;
-let SubtargetPredicate = HasMadMacF32Insts, isReMaterializable = 1 in
+let SubtargetPredicate = HasMadMacF32Insts, isReMaterializable = 1, FixedSize = 1 in
 def V_MADMK_F32 : VOP2_Pseudo <"v_madmk_f32", VOP_MADMK_F32, []>;
 
 let isCommutable = 1 in {
@@ -904,7 +904,7 @@ defm V_MAC_LEGACY_F32 : VOP2Inst <"v_mac_legacy_f32", VOP_MAC_LEGACY_F32>;
 } // End Constraints = "$vdst = $src2",
   //     isConvertibleToThreeAddress = 1
 
-let isReMaterializable = 1 in
+let isReMaterializable = 1, FixedSize = 1 in
 def V_MADAK_F32 : VOP2_Pseudo <"v_madak_f32", VOP_MADAK_F32, []>;
 } // End OtherPredicates = [HasMadMacF32Insts]
 } // End mayRaiseFPException = 0
@@ -1202,11 +1202,11 @@ let True16Predicate = UseFakeTrue16Insts in {
 
 let SubtargetPredicate = Has16BitInsts in {
 let isReMaterializable = 1 in {
-let FPDPRounding = 1 in {
+let FPDPRounding = 1, FixedSize = 1 in {
   def V_MADMK_F16 : VOP2_Pseudo <"v_madmk_f16", VOP_MADMK_F16, [], "">;
 } // End FPDPRounding = 1
 let isCommutable = 1 in {
-let mayRaiseFPException = 0 in {
+let mayRaiseFPException = 0, FixedSize = 1 in {
   def V_MADAK_F16 : VOP2_Pseudo <"v_madak_f16", VOP_MADAK_F16, [], "">;
 }
 let SubtargetPredicate = isGFX8GFX9 in {
diff --git a/llvm/test/CodeGen/AMDGPU/madmk-madak-encoding-size.ll b/llvm/test/CodeGen/AMDGPU/madmk-madak-encoding-size.ll
new file mode 100644
index 0000000000000..620afd2df4d1b
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/madmk-madak-encoding-size.ll
@@ -0,0 +1,34 @@
+; RUN: llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx803 -filetype=obj < %s | llvm-objdump --triple=amdgcn-amd-amdhsa --mcpu=gfx803 --disassemble - | FileCheck %s
+
+; Make sure computed instruction sizes for madak/madmk are correct and
+; pass the instruction size verifier.
+
+; CHECK: v_madak_f32 v0, v0, v1, 0x41200000 // 000000000004: 30000300 41200000
+define float @v_madak_f32(float %a, float %b) #0 {
+  %mul = fmul float %a, %b
+  %madmk = fadd float %mul, 10.0
+  ret float %madmk
+}
+
+; CHECK: v_madmk_f32 v0, v0, 0x41200000, v1 // 000000000044: 2E000300 41200000
+define float @v_madmk_f32(float %a, float %b) #0 {
+  %mul = fmul float %a, 10.0
+  %madmk = fadd float %mul, %b
+  ret float %madmk
+}
+
+; CHECK: v_madak_f16 v0, v0, v1, 0x4900 // 000000000084: 4A000300 00004900
+define half @v_madak_f16(half %a, half %b) #0 {
+  %mul = fmul half %a, %b
+  %madmk = fadd half %mul, 10.0
+  ret half %madmk
+}
+
+; CHECK: v_madmk_f16 v0, v0, 0x4900, v1 // 0000000000C4: 48000300 00004900
+define half @v_madmk_f16(half %a, half %b) #0 {
+  %mul = fmul half %a, 10.0
+  %madmk = fadd half %mul, %b
+  ret half %madmk
+}
+
+attributes #0 = { nounwind denormal_fpenv(preservesign) }