[llvm] [InstCombine] Fold chained GEP with constant base into single GEP (PR #170439)
Jianjian Guan via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 9 01:51:17 PST 2025
================
@@ -0,0 +1,162 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S -passes=instcombine | FileCheck %s
+
+define ptr @src_origin(i32 %arg0, ptr %arg1) {
+; CHECK-LABEL: @src_origin(
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[V1]], i64 63252, i64 29452
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i8, ptr [[ARG1:%.*]], i64 [[TMP1]]
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr i8, ptr %v0, i64 %v2
+ ret ptr %v3
+}
+
+define ptr @src_nuw(i32 %arg0, ptr %arg1) {
+; CHECK-LABEL: @src_nuw(
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[V1]], i64 63252, i64 29452
+; CHECK-NEXT: [[V3:%.*]] = getelementptr nuw i8, ptr [[ARG1:%.*]], i64 [[TMP1]]
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr nuw i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr nuw i8, ptr %v0, i64 %v2
+ ret ptr %v3
+}
+
+define ptr @src_inbounds_nuw(i32 %arg0, ptr %arg1) {
+; CHECK-LABEL: @src_inbounds_nuw(
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[V1]], i64 63252, i64 29452
+; CHECK-NEXT: [[V3:%.*]] = getelementptr nuw i8, ptr [[ARG1:%.*]], i64 [[TMP1]]
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr inbounds nuw i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr nuw i8, ptr %v0, i64 %v2
+ ret ptr %v3
+}
+
+define ptr @src_swap(i32 %arg0, ptr %arg1) {
+; CHECK-LABEL: @src_swap(
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[V2:%.*]] = select i1 [[V1]], i64 63252, i64 29452
+; CHECK-NEXT: [[V0:%.*]] = getelementptr i8, ptr [[ARG1:%.*]], i64 [[V2]]
+; CHECK-NEXT: ret ptr [[V0]]
+;
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v0 = getelementptr i8, ptr %arg1, i64 %v2
+ %v3 = getelementptr i8, ptr %v0, i64 8148
+ ret ptr %v3
+}
+
+; Fail 1: Different GEP type
+define ptr @src_fail_different_type(i32 %arg0, ptr %arg1) {
+; CHECK-LABEL: @src_fail_different_type(
+; CHECK-NEXT: [[V0:%.*]] = getelementptr inbounds nuw i8, ptr [[ARG1:%.*]], i64 8148
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[V2:%.*]] = select i1 [[V1]], i64 55104, i64 21304
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i16, ptr [[V0]], i64 [[V2]]
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr inbounds nuw i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr i16, ptr %v0, i64 %v2
+ ret ptr %v3
+}
+
+; Fail 2: No constant idx
+define ptr @src_fail_no_constant_idx(i32 %arg0, ptr %arg1, i64 %arg2) {
+; CHECK-LABEL: @src_fail_no_constant_idx(
+; CHECK-NEXT: [[V0:%.*]] = getelementptr inbounds nuw i8, ptr [[ARG1:%.*]], i64 [[ARG2:%.*]]
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[V2:%.*]] = select i1 [[V1]], i64 55104, i64 21304
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i8, ptr [[V0]], i64 [[V2]]
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr inbounds nuw i8, ptr %arg1, i64 %arg2
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr i8, ptr %v0, i64 %v2
+ ret ptr %v3
+}
+
+; Fail 3: Multiple use of select
+define ptr @src_fail_select_multiple_use(i32 %arg0, ptr %arg1, ptr %arg2) {
+; CHECK-LABEL: @src_fail_select_multiple_use(
+; CHECK-NEXT: [[V0:%.*]] = getelementptr inbounds nuw i8, ptr [[ARG1:%.*]], i64 8148
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[V2:%.*]] = select i1 [[V1]], i64 55104, i64 21304
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i8, ptr [[V0]], i64 [[V2]]
+; CHECK-NEXT: [[V4:%.*]] = getelementptr i8, ptr [[ARG2:%.*]], i64 [[V2]]
+; CHECK-NEXT: store ptr [[V3]], ptr [[V4]], align 8
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr inbounds nuw i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr i8, ptr %v0, i64 %v2
+ %v4 = getelementptr i8, ptr %arg2, i64 %v2
+ store ptr %v3, ptr %v4, align 8
+ ret ptr %v3
+}
+
+; Fail 4: Multiple use of source GEP
+define ptr @src_fail_source_gep_multiple_use(i32 %arg0, ptr %arg1, ptr %arg2) {
+; CHECK-LABEL: @src_fail_source_gep_multiple_use(
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[V1]], i64 63252, i64 29452
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i8, ptr [[ARG1:%.*]], i64 [[TMP1]]
+; CHECK-NEXT: [[V4:%.*]] = getelementptr i8, ptr [[ARG1]], i64 8248
+; CHECK-NEXT: store ptr [[V3]], ptr [[V4]], align 8
+; CHECK-NEXT: ret ptr [[V3]]
+;
+ %v0 = getelementptr inbounds nuw i8, ptr %arg1, i64 8148
+ %v1 = icmp sgt i32 %arg0, 3
+ %v2 = select i1 %v1, i64 55104, i64 21304
+ %v3 = getelementptr i8, ptr %v0, i64 %v2
+ %v4 = getelementptr i8, ptr %v0, i64 100
+ store ptr %v3, ptr %v4, align 8
+ ret ptr %v3
+}
+
+; TODO: constant vector index
+
+define <2 x ptr> @fail_vector_const_vector_select(i32 %arg0, <2 x ptr> %arg1) {
+; CHECK-LABEL: @fail_vector_const_vector_select(
+; CHECK-NEXT: [[V0:%.*]] = getelementptr i8, <2 x ptr> [[ARG1:%.*]], <2 x i64> <i64 8148, i64 8848>
+; CHECK-NEXT: [[V1:%.*]] = icmp sgt i32 [[ARG0:%.*]], 3
+; CHECK-NEXT: [[V2:%.*]] = select i1 [[V1]], <2 x i64> <i64 55104, i64 56654>, <2 x i64> <i64 21304, i64 21224>
+; CHECK-NEXT: [[V3:%.*]] = getelementptr i8, <2 x ptr> [[V0]], <2 x i64> [[V2]]
+; CHECK-NEXT: ret <2 x ptr> [[V3]]
+;
+ %v0 = getelementptr i8, <2 x ptr> %arg1, <2 x i64> <i64 8148, i64 8848>
----------------
jacquesguan wrote:
Added.
https://github.com/llvm/llvm-project/pull/170439
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