diff options
Diffstat (limited to 'source')
| -rw-r--r-- | source/slang/ir-ssa.cpp | 77 | ||||
| -rw-r--r-- | source/slang/slang.natvis | 9 |
2 files changed, 65 insertions, 21 deletions
diff --git a/source/slang/ir-ssa.cpp b/source/slang/ir-ssa.cpp index 207938a90..973030852 100644 --- a/source/slang/ir-ssa.cpp +++ b/source/slang/ir-ssa.cpp @@ -572,6 +572,43 @@ void maybeSealBlock( blockInfo->isSealed = true; } +// In some cases we may have a pointer to an IR value that +// represents a phi node that has been replaced with another +// IR value, because we discovered that the phi is no longer +// needed. +// +// The `maybeGetPhiReplacement` function will follow any +// chain of replacements that might be present, so that we +// don't end up referencing a dangling/unused value in +// the code that we generate. +// +IRInst* maybeGetPhiReplacement( + ConstructSSAContext* context, + IRInst* inVal) +{ + IRInst* val = inVal; + + while( val->op == kIROp_Param ) + { + // The value is a parameter, but is it a phi? + IRParam* maybePhi = (IRParam*) val; + RefPtr<PhiInfo> phiInfo = nullptr; + if(!context->phiInfos.TryGetValue(maybePhi, phiInfo)) + break; + + // Okay, this is indeed a phi we are adding, but + // is it one that got replaced? + if(!phiInfo->replacement) + break; + + // The phi we want to use got replaced, so we + // had better use the replacement instead. + val = phiInfo->replacement; + } + + return val; +} + IRInst* readVarRec( ConstructSSAContext* context, SSABlockInfo* blockInfo, @@ -664,10 +701,24 @@ IRInst* readVarRec( // value for the given variable in this block writeVar(context, blockInfo, var, val); + // If `val` represents a phi node (block parameter) then + // it is possible that some of the operations above might + // have caused it to be replaced with another value, + // and in that case we had better not return it to + // be referenced in user code. + // + // Note: it is okay for the `valueForVar` map that + // we update in `writeVar` to use the old value, so long + // as we do this replacement logic anywhere we might read + // from that map. + // + val = maybeGetPhiReplacement(context, val); + return val; } + IRInst* readVar( ConstructSSAContext* context, SSABlockInfo* blockInfo, @@ -682,27 +733,11 @@ IRInst* readVar( // Hooray, we found a value to use, and we // can proceed without too many complications. - // Well, let's check for one special case here, which - // is when the value we intend to use is a `phi` - // node that we ultimately decided to remove. - while( val->op == kIROp_Param ) - { - // The value is a parameter, but is it a phi? - IRParam* maybePhi = (IRParam*) val; - RefPtr<PhiInfo> phiInfo = nullptr; - if(!context->phiInfos.TryGetValue(maybePhi, phiInfo)) - break; - - // Okay, this is indeed a phi we are adding, but - // is it one that got replaced? - if(!phiInfo->replacement) - break; - - // The phi we want to use got replaced, so we - // had better use the replacement instead. - val = phiInfo->replacement; - } - + // Just like in the `readVarRec` case above, we need + // to handle the case where `val` might represent + // a phi node that has subsequently been replaced. + // + val = maybeGetPhiReplacement(context, val); return val; } diff --git a/source/slang/slang.natvis b/source/slang/slang.natvis index bb3d3a16c..247064f3a 100644 --- a/source/slang/slang.natvis +++ b/source/slang/slang.natvis @@ -93,6 +93,15 @@ </Expand> </Synthetic> <Item Name="[parent]">parent</Item> + <Synthetic Name="[children]" Condition="(op >= Slang::kIROp_FirstParentInst) && (op <= Slang::kIROp_LastParentInst)"> + <Expand> + <LinkedListItems> + <HeadPointer>(*((Slang::IRParentInst*) this)).children.first</HeadPointer> + <NextPointer>next</NextPointer> + <ValueNode>this</ValueNode> + </LinkedListItems> + </Expand> + </Synthetic> <Synthetic Name="[uses]"> <Expand> <LinkedListItems> |