From 225ae82fdbbff7d22fbbf9aead00e67e08416ecf Mon Sep 17 00:00:00 2001
From: SahilPatidar <patidarsahil2001@gmail.com>
Date: Sat, 20 Apr 2024 14:15:14 +0530
Subject: [PATCH] [InstCombine] fold `cond ? x : -x == 0` into `x == 0`
 (#85673)

Resolve #85250
Alive2: https://alive2.llvm.org/ce/z/7DMRCy
---
 .../InstCombine/InstCombineCompares.cpp       |   8 +
 llvm/test/Transforms/InstCombine/fcmp.ll      | 232 ++++++++++++++++++
 2 files changed, 240 insertions(+)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index fdadf729fbd541..f0278f207549fa 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -8045,6 +8045,14 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
   Constant *RHSC;
   if (match(Op0, m_Instruction(LHSI)) && match(Op1, m_Constant(RHSC))) {
     switch (LHSI->getOpcode()) {
+    case Instruction::Select:
+      // fcmp eq (cond ? x : -x), 0 --> fcmp eq x, 0
+      if (FCmpInst::isEquality(Pred) && match(RHSC, m_AnyZeroFP()) &&
+          (match(LHSI,
+                 m_Select(m_Value(), m_Value(X), m_FNeg(m_Deferred(X)))) ||
+           match(LHSI, m_Select(m_Value(), m_FNeg(m_Value(X)), m_Deferred(X)))))
+        return replaceOperand(I, 0, X);
+      break;
     case Instruction::PHI:
       if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))
         return NV;
diff --git a/llvm/test/Transforms/InstCombine/fcmp.ll b/llvm/test/Transforms/InstCombine/fcmp.ll
index 389264e2f70759..4d907800219d63 100644
--- a/llvm/test/Transforms/InstCombine/fcmp.ll
+++ b/llvm/test/Transforms/InstCombine/fcmp.ll
@@ -1486,3 +1486,235 @@ define i1 @fcmp_fadd_fast_zero(float %x, float %y) {
   %cmp = fcmp ugt float %add, %y
   ret i1 %cmp
 }
+
+define i1 @fcmp_ueq_sel_x_negx(float %x) {
+; CHECK-LABEL: @fcmp_ueq_sel_x_negx(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp ueq float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp ueq float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp ueq float %sel, 0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_une_sel_x_negx(float %x) {
+; CHECK-LABEL: @fcmp_une_sel_x_negx(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp une float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp une float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp une float %sel, 0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_oeq_sel_x_negx(float %x) {
+; CHECK-LABEL: @fcmp_oeq_sel_x_negx(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp oeq float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp oeq float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp oeq float %sel, 0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_one_sel_x_negx(float %x) {
+; CHECK-LABEL: @fcmp_one_sel_x_negx(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp one float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp one float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp one float %sel, 0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_ueq_sel_x_negx_nzero(float %x) {
+; CHECK-LABEL: @fcmp_ueq_sel_x_negx_nzero(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp ueq float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp ueq float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp ueq float %sel, -0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_une_sel_x_negx_nzero(float %x) {
+; CHECK-LABEL: @fcmp_une_sel_x_negx_nzero(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp une float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp une float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp une float %sel, -0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_oeq_sel_x_negx_nzero(float %x) {
+; CHECK-LABEL: @fcmp_oeq_sel_x_negx_nzero(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp oeq float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp oeq float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp oeq float %sel, -0.000000e+00
+  ret i1 %res
+}
+
+define i1 @fcmp_one_sel_x_negx_nzero(float %x) {
+; CHECK-LABEL: @fcmp_one_sel_x_negx_nzero(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp one float [[X:%.*]], 0.000000e+00
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %f = fcmp one float %x, 0.000000e+00
+  %neg = fneg float %x
+  %sel = select i1 %f, float %x, float %neg
+  %res = fcmp one float %sel, -0.000000e+00
+  ret i1 %res
+}
+
+define <8 x i1> @fcmp_ueq_sel_x_negx_vec(<8 x float> %x) {
+; CHECK-LABEL: @fcmp_ueq_sel_x_negx_vec(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp ueq <8 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[RES]]
+;
+  %f = fcmp ueq <8 x float> %x, zeroinitializer
+  %neg = fneg <8 x float> %x
+  %sel = select <8 x i1> %f, <8 x float> %x, <8 x float> %neg
+  %res = fcmp ueq <8 x float> %sel, zeroinitializer
+  ret <8 x i1> %res
+}
+
+define <8 x i1> @fcmp_une_sel_x_negx_vec(<8 x float> %x) {
+; CHECK-LABEL: @fcmp_une_sel_x_negx_vec(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp une <8 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[RES]]
+;
+  %f = fcmp une <8 x float> %x, zeroinitializer
+  %neg = fneg <8 x float> %x
+  %sel = select <8 x i1> %f, <8 x float> %x, <8 x float> %neg
+  %res = fcmp une <8 x float> %sel, zeroinitializer
+  ret <8 x i1> %res
+}
+
+define <8 x i1> @fcmp_oeq_sel_x_negx_vec(<8 x float> %x) {
+; CHECK-LABEL: @fcmp_oeq_sel_x_negx_vec(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp oeq <8 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[RES]]
+;
+  %f = fcmp oeq <8 x float> %x, zeroinitializer
+  %neg = fneg <8 x float> %x
+  %sel = select <8 x i1> %f, <8 x float> %x, <8 x float> %neg
+  %res = fcmp oeq <8 x float> %sel, zeroinitializer
+  ret <8 x i1> %res
+}
+
+define <8 x i1> @fcmp_one_sel_x_negx_vec(<8 x float> %x) {
+; CHECK-LABEL: @fcmp_one_sel_x_negx_vec(
+; CHECK-NEXT:    [[RES:%.*]] = fcmp one <8 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <8 x i1> [[RES]]
+;
+  %f = fcmp one <8 x float> %x, zeroinitializer
+  %neg = fneg <8 x float> %x
+  %sel = select <8 x i1> %f, <8 x float> %x, <8 x float> %neg
+  %res = fcmp one <8 x float> %sel, zeroinitializer
+  ret <8 x i1> %res
+}
+
+define <2 x i1> @fcmp_oeq_sel_x_negx_with_any_fpzero_ninf_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_oeq_sel_x_negx_with_any_fpzero_ninf_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp ninf oeq <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp ninf oeq <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_one_sel_x_negx_with_any_fpzero_ninf_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_one_sel_x_negx_with_any_fpzero_ninf_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp ninf one <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp ninf one <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_ueq_sel_x_negx_with_any_fpzero_ninf_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_ueq_sel_x_negx_with_any_fpzero_ninf_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp ninf ueq <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp ninf ueq <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_une_sel_x_negx_with_any_fpzero_ninf_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_une_sel_x_negx_with_any_fpzero_ninf_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp ninf une <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp ninf une <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_oeq_sel_x_negx_with_any_fpzero_nnan_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_oeq_sel_x_negx_with_any_fpzero_nnan_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp nnan oeq <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp nnan oeq <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_one_sel_x_negx_with_any_fpzero_nnan_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_one_sel_x_negx_with_any_fpzero_nnan_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp nnan one <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp nnan one <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_ueq_sel_x_negx_with_any_fpzero_nnan_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_ueq_sel_x_negx_with_any_fpzero_nnan_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp nnan ueq <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp nnan ueq <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}
+
+define <2 x i1> @fcmp_une_sel_x_negx_with_any_fpzero_nnan_vec(<2 x i1> %cond, <2 x float> %x) {
+; CHECK-LABEL: @fcmp_une_sel_x_negx_with_any_fpzero_nnan_vec(
+; CHECK-NEXT:    [[ICMP:%.*]] = fcmp nnan une <2 x float> [[X:%.*]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[ICMP]]
+;
+  %fneg = fneg <2 x float> %x
+  %sel = select <2 x i1> %cond, <2 x float> %x, <2 x float> %fneg
+  %icmp = fcmp nnan une <2 x float> %sel, <float 0.0, float -0.0>
+  ret <2 x i1> %icmp
+}