From c0cd25ba76d23fc6b1ce04302994a4b4bc89c168 Mon Sep 17 00:00:00 2001
From: Mihail Moskov <28909106+corleypc@users.noreply.github.com>
Date: Wed, 9 Sep 2026 17:13:20 +0300
Subject: [PATCH] simd_abs optimization + fix for unsigned

---
 src/llvm_backend_proc.cpp    | 19 +++++++++++--------
 tests/internal/test_abs.odin | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/src/llvm_backend_proc.cpp b/src/llvm_backend_proc.cpp
index f7e4ebe69..c662a0a95 100644
--- a/src/llvm_backend_proc.cpp
+++ b/src/llvm_backend_proc.cpp
@@ -1816,15 +1816,18 @@ gb_internal lbValue lb_build_builtin_simd_proc(lbProcedure *p, Ast *expr, TypeAn
 		return res;
 	case BuiltinProc_simd_abs:
 		if (is_float) {
-			LLVMValueRef pos = arg0.value;
-			LLVMValueRef neg = LLVMBuildFNeg(p->builder, pos, "");
-			LLVMValueRef cond = LLVMBuildFCmp(p->builder, LLVMRealOGT, pos, neg, "");
-			res.value = LLVMBuildSelect(p->builder, cond, pos, neg, "");
+			LLVMTypeRef types[1] = {LLVMTypeOf(arg0.value)};
+			LLVMValueRef args[1] = {arg0.value};
+			res.value = lb_call_intrinsic(p, "llvm.fabs", args, gb_count_of(args), types, gb_count_of(types));
+		} else if (is_signed) {
+			LLVMTypeRef types[1] = {LLVMTypeOf(arg0.value)};
+			// is_int_min_poison=false, so abs(min(T)) = min(T) and not poison
+			LLVMValueRef is_int_min_poison = lb_const_bool(p->module, t_llvm_bool, false).value;
+			LLVMValueRef args[2] = {arg0.value, is_int_min_poison};
+			res.value = lb_call_intrinsic(p, "llvm.abs", args, gb_count_of(args), types, gb_count_of(types));
 		} else {
-			LLVMValueRef pos = arg0.value;
-			LLVMValueRef neg = LLVMBuildNeg(p->builder, pos, "");
-			LLVMValueRef cond = LLVMBuildICmp(p->builder, is_signed ? LLVMIntSGT : LLVMIntUGT, pos, neg, "");
-			res.value = LLVMBuildSelect(p->builder, cond, pos, neg, "");
+			// unsigned integers -> |x| = x
+			res.value = arg0.value;
 		}
 		return res;
 	case BuiltinProc_simd_min:
diff --git a/tests/internal/test_abs.odin b/tests/internal/test_abs.odin
index 56db10c09..347ab5ac0 100644
--- a/tests/internal/test_abs.odin
+++ b/tests/internal/test_abs.odin
@@ -1,5 +1,6 @@
 package test_internal
 
+import "base:intrinsics"
 import "core:testing"
 
 @(private="file")
@@ -166,3 +167,26 @@ abs_f64_variable :: proc(t: ^testing.T) {
 	testing.expect_value(t, abs(not_const(max(f64be))), max(f64be))
 	testing.expect_value(t, abs(not_const(f64be(-.12345))), .12345)
 }
+
+@(test)
+simd_abs_variable :: proc(t: ^testing.T) {
+	// signed ints -> abs(min(T)) wraps to min(T)
+	i32x4 := intrinsics.simd_abs(not_const(#simd[4]i32{min(i32), -1, 0, max(i32)}))
+	testing.expect_value(t, transmute([4]i32)i32x4, [4]i32{min(i32), 1, 0, max(i32)})
+	i8x16 := intrinsics.simd_abs(not_const(#simd[16]i8{min(i8), -1, 0, max(i8), -2, 2, -3, 3, -4, 4, -5, 5, -6, 6, -7, 7}))
+	testing.expect_value(t, transmute([16]i8)i8x16, [16]i8{min(i8), 1, 0, max(i8), 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7})
+
+	// unsigned ints
+	u32x4 := intrinsics.simd_abs(not_const(#simd[4]u32{0, 1, 100, max(u32)}))
+	testing.expect_value(t, transmute([4]u32)u32x4, [4]u32{0, 1, 100, max(u32)})
+	u8x16 := intrinsics.simd_abs(not_const(#simd[16]u8{0, 1, 100, 200, 255, 128, 127, 2, 3, 4, 5, 6, 7, 8, 9, 10}))
+	testing.expect_value(t, transmute([16]u8)u8x16, [16]u8{0, 1, 100, 200, 255, 128, 127, 2, 3, 4, 5, 6, 7, 8, 9, 10})
+
+	// floats
+	f32x4 := intrinsics.simd_abs(not_const(#simd[4]f32{0., -0., -1., -.12345}))
+	f32_expected := [4]f32{0., 0., 1., .12345}
+	testing.expect_value(t, transmute([4]u32)f32x4, transmute([4]u32)f32_expected)
+	f64x2 := intrinsics.simd_abs(not_const(#simd[2]f64{-0., min(f64)}))
+	f64_expected := [2]f64{0., max(f64)}
+	testing.expect_value(t, transmute([2]u64)f64x2, transmute([2]u64)f64_expected)
+}