Relax the inst definition order rule (#8588)

Close #8572.

The root cause of the issue is that in `_replaceInstUsesWith` call,
if the use of the inst is a generic parameter, and the inst is the data
type of that generic parameter, we could end up of moving the data type
before the generic parameter. This will break the layout of generic
parameters, where all the generic parameters should be laid consecutively
at the beginning of the first block of the generic.

Therefore, we don't make that relocation for such case.

1 files changed, 5 insertions, 1 deletions

diff --git a/source/slang/slang-ir-validate.cpp b/source/slang/slang-ir-validate.cpp
index 55f3ad227..e7bb7b548 100644
--- a/source/slang/slang-ir-validate.cpp
+++ b/source/slang/slang-ir-validate.cpp
@@ -201,9 +201,13 @@ void validateIRInstOperand(IRValidateContext* context, IRInst* inst, IRUse* oper
                 // in order.
                 if (context)
                 {
+                    // There is exception that the use of an inst is defined before the inst,
+                    // e.g. generic parameter can be defined before its data type in some cases.
+                    // In those cases we allow relaxing the rule.
                     validate(
                         context,
-                        context->seenInsts.contains(operandValue),
+                        context->seenInsts.contains(operandValue) ||
+                            canRelaxInstOrderRule(operandValue, inst),
                         inst,
                         "def must come before use in same block");
                 }