[llvm] [AMDGPU] Form V_MAD_U64_U32 from mul24/mulhi24 (PR #72393)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Pierre van Houtryve (Pierre-vh)

<details>
<summary>Changes</summary>

CGP can transform a fine mul+add into a (mul24/mulhi24)+add, so add a pattern for that.

See SWDEV-421067

---
Full diff: https://github.com/llvm/llvm-project/pull/72393.diff


2 Files Affected:

- (modified) llvm/lib/Target/AMDGPU/VOP3Instructions.td (+9) 
- (modified) llvm/test/CodeGen/AMDGPU/integer-mad-patterns.ll (+63) 


``````````diff
diff --git a/llvm/lib/Target/AMDGPU/VOP3Instructions.td b/llvm/lib/Target/AMDGPU/VOP3Instructions.td
index 114d33b077866a1..06856b03a508124 100644
--- a/llvm/lib/Target/AMDGPU/VOP3Instructions.td
+++ b/llvm/lib/Target/AMDGPU/VOP3Instructions.td
@@ -676,6 +676,15 @@ multiclass IMAD32_Pats <VOP3_Pseudo inst> {
         (ThreeOpFragSDAG<mul, add> i32:$src0, i32:$src1, (i32 imm:$src2)),
         (EXTRACT_SUBREG (inst $src0, $src1, (i64 (as_i64imm $src2)), 0 /* clamp */), sub0)
         >;
+
+  // Handle cases where amdgpu-codegenprepare-mul24 made a mul24 instead of a normal mul.
+  def : GCNPat <
+      (i64 (add (bitconvert (v2i32 (build_vector
+                                     (AMDGPUmul_u24 i32:$src0, i32:$src1),
+                                     (AMDGPUmulhi_u24 i32:$src0, i32:$src1)))),
+                i64:$src2)),
+      (inst $src0, $src1, $src2, 0 /* clamp */)
+      >;
 }
 
 // exclude pre-GFX9 where it was slow
diff --git a/llvm/test/CodeGen/AMDGPU/integer-mad-patterns.ll b/llvm/test/CodeGen/AMDGPU/integer-mad-patterns.ll
index 61017e809c86365..56b6fef1b82255c 100644
--- a/llvm/test/CodeGen/AMDGPU/integer-mad-patterns.ll
+++ b/llvm/test/CodeGen/AMDGPU/integer-mad-patterns.ll
@@ -6928,6 +6928,69 @@ entry:
   ret <2 x i16> %add0
 }
 
+define i64 @mul_mulhi_u24(i32 %x, i32 %y, i64 %z) {
+; GFX67-LABEL: mul_mulhi_u24:
+; GFX67:       ; %bb.0:
+; GFX67-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX67-NEXT:    v_mul_u32_u24_e32 v4, v0, v1
+; GFX67-NEXT:    v_mul_hi_u32_u24_e32 v1, v0, v1
+; GFX67-NEXT:    v_add_i32_e32 v0, vcc, v4, v2
+; GFX67-NEXT:    v_addc_u32_e32 v1, vcc, v1, v3, vcc
+; GFX67-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX8-LABEL: mul_mulhi_u24:
+; GFX8:       ; %bb.0:
+; GFX8-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX8-NEXT:    v_mul_u32_u24_e32 v4, v0, v1
+; GFX8-NEXT:    v_mul_hi_u32_u24_e32 v1, v0, v1
+; GFX8-NEXT:    v_add_u32_e32 v0, vcc, v4, v2
+; GFX8-NEXT:    v_addc_u32_e32 v1, vcc, v1, v3, vcc
+; GFX8-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX9-SDAG-LABEL: mul_mulhi_u24:
+; GFX9-SDAG:       ; %bb.0:
+; GFX9-SDAG-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX9-SDAG-NEXT:    v_mad_u64_u32 v[0:1], s[4:5], v0, v1, v[2:3]
+; GFX9-SDAG-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX9-GISEL-LABEL: mul_mulhi_u24:
+; GFX9-GISEL:       ; %bb.0:
+; GFX9-GISEL-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX9-GISEL-NEXT:    v_mul_u32_u24_e32 v4, v0, v1
+; GFX9-GISEL-NEXT:    v_mul_hi_u32_u24_e32 v1, v0, v1
+; GFX9-GISEL-NEXT:    v_add_co_u32_e32 v0, vcc, v4, v2
+; GFX9-GISEL-NEXT:    v_addc_co_u32_e32 v1, vcc, v1, v3, vcc
+; GFX9-GISEL-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX10-SDAG-LABEL: mul_mulhi_u24:
+; GFX10-SDAG:       ; %bb.0:
+; GFX10-SDAG-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX10-SDAG-NEXT:    v_mad_u64_u32 v[0:1], null, v0, v1, v[2:3]
+; GFX10-SDAG-NEXT:    s_setpc_b64 s[30:31]
+;
+; GFX10-GISEL-LABEL: mul_mulhi_u24:
+; GFX10-GISEL:       ; %bb.0:
+; GFX10-GISEL-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GFX10-GISEL-NEXT:    v_mul_u32_u24_e32 v4, v0, v1
+; GFX10-GISEL-NEXT:    v_mul_hi_u32_u24_e32 v1, v0, v1
+; GFX10-GISEL-NEXT:    v_add_co_u32 v0, vcc_lo, v4, v2
+; GFX10-GISEL-NEXT:    v_add_co_ci_u32_e32 v1, vcc_lo, v1, v3, vcc_lo
+; GFX10-GISEL-NEXT:    s_setpc_b64 s[30:31]
+  %mul = call i32 @llvm.amdgcn.mul.u24(i32 %x, i32 %y)
+  %mulhi = call i32 @llvm.amdgcn.mulhi.u24(i32 %x, i32 %y)
+  %mul.zext = zext i32 %mul to i64
+  %mulhi.zext = zext i32 %mulhi to i64
+  %mulhi.shift = shl i64 %mulhi.zext, 32
+  %mul.mulhi = or i64 %mulhi.shift, %mul.zext
+  %add = add nuw nsw i64 %mul.mulhi, %z
+  ret i64 %add
+}
+
+declare i32 @llvm.amdgcn.mul.u24(i32, i32)
+declare i32 @llvm.amdgcn.mulhi.u24(i32, i32)
+declare i32 @llvm.amdgcn.mul.i24(i32, i32)
+declare i32 @llvm.amdgcn.mulhi.i24(i32, i32)
+
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; GFX6: {{.*}}
 ; GFX7: {{.*}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/72393