[llvm] [InstCombine] Add tests for fdiv by splat of pow/exp/powi. NFC (PR #227237)
Harrison Hao via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 29 04:16:58 PDT 2026
https://github.com/harrisonGPU updated https://github.com/llvm/llvm-project/pull/227237
>From 16795b9e01c0e88baf451f06c0744cfa9dd0094b Mon Sep 17 00:00:00 2001
From: Harrison Hao <tsworld1314 at gmail.com>
Date: Tue, 29 Sep 2026 16:56:30 +0800
Subject: [PATCH] [InstCombine] Add tests for fdiv by splat of pow/exp/powi
(NFC)
Pre-commit tests for folding fdiv whose divisor is a splat of a scalar
pow/exp/exp2/powi.
---
llvm/test/Transforms/InstCombine/fdiv.ll | 196 +++++++++++++++++++++++
1 file changed, 196 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/fdiv.ll b/llvm/test/Transforms/InstCombine/fdiv.ll
index e992ba59b85746..212d1e15e76b5b 100644
--- a/llvm/test/Transforms/InstCombine/fdiv.ll
+++ b/llvm/test/Transforms/InstCombine/fdiv.ll
@@ -937,6 +937,202 @@ define <2 x half> @powi_recip(<2 x half> %x, i32 %y) {
ret <2 x half> %r
}
+declare void @use_v2f32(<2 x float>)
+
+define <2 x float> @pow_divisor_splat(float %x, float %y, <2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+define <vscale x 2 x float> @pow_divisor_splat_scalable(float %x, float %y, <vscale x 2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat_scalable(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <vscale x 2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <vscale x 2 x float> [[INS]], <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <vscale x 2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <vscale x 2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <vscale x 2 x float> poison, float %p, i64 0
+ %splat = shufflevector <vscale x 2 x float> %ins, <vscale x 2 x float> poison, <vscale x 2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <vscale x 2 x float> %z, %splat
+ ret <vscale x 2 x float> %r
+}
+
+; Negative test - don't create an extra pow
+
+define <2 x float> @pow_divisor_splat_extra_use(float %x, float %y, <2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat_extra_use(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: call void @use_f32(float [[P]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ call void @use_f32(float %p)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+; Negative test - don't create an extra splat
+
+define <2 x float> @pow_divisor_splat_extra_use_insert(float %x, float %y, <2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat_extra_use_insert(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: call void @use_v2f32(<2 x float> [[INS]])
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ call void @use_v2f32(<2 x float> %ins)
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+; Negative test - don't create an extra splat
+
+define <2 x float> @pow_divisor_splat_extra_use_shuffle(float %x, float %y, <2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat_extra_use_shuffle(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: call void @use_v2f32(<2 x float> [[SPLAT]])
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ call void @use_v2f32(<2 x float> %splat)
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+; Negative test - must have reassoc+arcp
+
+define <2 x float> @pow_divisor_splat_not_enough_fmf(float %x, float %y, <2 x float> %z) {
+; CHECK-LABEL: @pow_divisor_splat_not_enough_fmf(
+; CHECK-NEXT: [[P:%.*]] = call fast float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call fast float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+; Negative test - a splat constant divisor is not an instruction
+
+define <2 x float> @splat_constexpr_divisor(<2 x float> %z) {
+; CHECK-LABEL: @splat_constexpr_divisor(
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], <float bitcast (i32 ptrtoint (ptr @use_f32 to i32) to float), float bitcast (i32 ptrtoint (ptr @use_f32 to i32) to float)>
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %r = fdiv reassoc arcp <2 x float> %z, <float bitcast (i32 ptrtoint (ptr @use_f32 to i32) to float), float bitcast (i32 ptrtoint (ptr @use_f32 to i32) to float)>
+ ret <2 x float> %r
+}
+
+; Special-case - reciprocal does not require extra fmul
+
+define <2 x float> @pow_recip_splat(float %x, float %y) {
+; CHECK-LABEL: @pow_recip_splat(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.pow.f32(float [[X:%.*]], float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[TMP1:%.*]] = fdiv reassoc arcp <2 x float> <float 1.000000e+00, float poison>, [[INS]]
+; CHECK-NEXT: [[R:%.*]] = shufflevector <2 x float> [[TMP1]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.pow.f32(float %x, float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> splat (float 1.0), %splat
+ ret <2 x float> %r
+}
+
+define <2 x float> @exp_divisor_splat(float %y, <2 x float> %z) {
+; CHECK-LABEL: @exp_divisor_splat(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.exp.f32(float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.exp.f32(float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+define <2 x float> @exp2_divisor_splat(float %y, <2 x float> %z) {
+; CHECK-LABEL: @exp2_divisor_splat(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.exp2.f32(float [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.exp2.f32(float %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+define <2 x float> @powi_divisor_splat(float %x, i32 %y, <2 x float> %z) {
+; CHECK-LABEL: @powi_divisor_splat(
+; CHECK-NEXT: [[P:%.*]] = call float @llvm.powi.f32.i32(float [[X:%.*]], i32 [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc ninf arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call float @llvm.powi.f32.i32(float %x, i32 %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp ninf <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
+; Negative test - must have reassoc+arcp+ninf
+
+define <2 x float> @powi_divisor_splat_not_enough_fmf(float %x, i32 %y, <2 x float> %z) {
+; CHECK-LABEL: @powi_divisor_splat_not_enough_fmf(
+; CHECK-NEXT: [[P:%.*]] = call fast float @llvm.powi.f32.i32(float [[X:%.*]], i32 [[Y:%.*]])
+; CHECK-NEXT: [[INS:%.*]] = insertelement <2 x float> poison, float [[P]], i64 0
+; CHECK-NEXT: [[SPLAT:%.*]] = shufflevector <2 x float> [[INS]], <2 x float> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT: [[R:%.*]] = fdiv reassoc arcp <2 x float> [[Z:%.*]], [[SPLAT]]
+; CHECK-NEXT: ret <2 x float> [[R]]
+;
+ %p = call fast float @llvm.powi.f32.i32(float %x, i32 %y)
+ %ins = insertelement <2 x float> poison, float %p, i64 0
+ %splat = shufflevector <2 x float> %ins, <2 x float> poison, <2 x i32> zeroinitializer
+ %r = fdiv reassoc arcp <2 x float> %z, %splat
+ ret <2 x float> %r
+}
+
define float @fdiv_zero_f32(float %x) {
; CHECK-LABEL: @fdiv_zero_f32(
; CHECK-NEXT: [[FDIV:%.*]] = fdiv float [[X:%.*]], 0.000000e+00
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