Be more careful about merge blocks during loop inversion (#3136)

* fix block eater

* Be more careful about merge blocks during loop inversion

* Restrict loop inversion to loops without continue jumps

* Remove multiple back-edges from loops for SPIR-V

* Wiggle cross compile test output

* Make loop-inversion more conservative

* Allow loops on false side in cfg normalization

* Do not set loop continue block during inversion

* Add loop inversion test to failing test list for spirv

* Simplify single use continue blocks in spirv legalization

* wobble expected failure list

---------

Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 5 insertions, 7 deletions

diff --git a/source/slang/slang-ir-loop-unroll.cpp b/source/slang/slang-ir-loop-unroll.cpp
index 36a2abbfc..c9ac4191b 100644
--- a/source/slang/slang-ir-loop-unroll.cpp
+++ b/source/slang/slang-ir-loop-unroll.cpp
@@ -174,11 +174,8 @@ static void _foldAndSimplifyLoopIteration(
             auto b = clonedBlocks[i];
             if (b)
             {
-                if (i != insertIndex)
-                {
-                    clonedBlocks[insertIndex] = b;
-                    insertIndex++;
-                }
+                clonedBlocks[insertIndex] = b;
+                insertIndex++;
             }
         }
         clonedBlocks.setCount(insertIndex);
@@ -554,11 +551,12 @@ void eliminateContinueBlocks(IRModule* module, IRLoop* loopInst)
     //  where a continue is replaced with a "break" into breakableRegionBreakBlock.
     //
 
-    if (loopInst->getContinueBlock() == loopInst->getTargetBlock())
+    auto continueBlock = loopInst->getContinueBlock();
+
+    if (continueBlock == loopInst->getTargetBlock())
         return;
 
     // If the continue block is not reachable, remove it.
-    auto continueBlock = loopInst->getContinueBlock();
     if (continueBlock && !continueBlock->hasMoreThanOneUse())
     {
         loopInst->continueBlock.set(loopInst->getTargetBlock());