From 910fc6e364a12bbe5f2328de4c610220c834829f Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Mon, 3 Mar 2025 01:21:01 +0100
Subject: [PATCH] Post and pre-decrement operators switched places for vector
 elements. #2010.

---
 releasenotes.md                       |  1 +
 src/compiler/llvm_codegen_expr.c      |  2 +-
 test/test_suite/vector/vector_inc.c3t | 20 ++++++++++++++++++++
 test/unit/regression/inc_dec.c3       |  2 +-
 4 files changed, 23 insertions(+), 2 deletions(-)
 create mode 100644 test/test_suite/vector/vector_inc.c3t

diff --git a/releasenotes.md b/releasenotes.md
index 19ce0ab71..ab191f07c 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -18,6 +18,7 @@
 
 ### Fixes
 - Fix address sanitizer to work on MachO targets (e.g. MacOS).
+- Post and pre-decrement operators switched places for vector elements #2010.
 
 ### Stdlib changes
 - `new_*` functions in general moved to version without `new_` prefix.
diff --git a/src/compiler/llvm_codegen_expr.c b/src/compiler/llvm_codegen_expr.c
index 99e62c82a..02bf2992d 100644
--- a/src/compiler/llvm_codegen_expr.c
+++ b/src/compiler/llvm_codegen_expr.c
@@ -2247,7 +2247,7 @@ static inline void llvm_emit_pre_post_inc_dec_vector(GenContext *c, BEValue *val
 	llvm_store_raw(c, &addr, vector);
 
 	// And set the return value.
-	llvm_value_set(value, pre ? current_res.value : new_value, element);
+	llvm_value_set(value, pre ? new_value : current_res.value, element);
 }
 
 /**
diff --git a/test/test_suite/vector/vector_inc.c3t b/test/test_suite/vector/vector_inc.c3t
new file mode 100644
index 000000000..f3b4d2827
--- /dev/null
+++ b/test/test_suite/vector/vector_inc.c3t
@@ -0,0 +1,20 @@
+// #target: macos-x64
+module test;
+fn void main()
+{
+    float[<1>] myvar = { 3 };
+    myvar.x = ++myvar.x * 2;
+}
+
+/* #expect: test.ll
+
+  %0 = load <1 x float>, ptr %myvar, align 4
+  %1 = load <1 x float>, ptr %myvar, align 4
+  %2 = extractelement <1 x float> %1, i64 0
+  %fincdec = fadd float %2, 1.000000e+00
+  %3 = insertelement <1 x float> %1, float %fincdec, i64 0
+  store <1 x float> %3, ptr %myvar, align 4
+  %fmul = fmul float %fincdec, 2.000000e+00
+  %elemset = insertelement <1 x float> %0, float %fmul, i64 0
+  store <1 x float> %elemset, ptr %myvar, align 4
+  ret void
diff --git a/test/unit/regression/inc_dec.c3 b/test/unit/regression/inc_dec.c3
index 3118df781..4e7446855 100644
--- a/test/unit/regression/inc_dec.c3
+++ b/test/unit/regression/inc_dec.c3
@@ -9,7 +9,7 @@ fn void vector_inc_dec() @test
 	int[<3>] g = x--;
 	assert(x == { 0, 0, -1 });
 	assert(y == { 1, 0, 1 });
-	assert(z == 0 && zz == 1);
+	assert(z == 1 && zz == 0);
 	assert(g == { 1, 1, 0 });
 }