diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/passes/RemoveUnusedModuleElements.cpp | 36 |
1 files changed, 31 insertions, 5 deletions
diff --git a/src/passes/RemoveUnusedModuleElements.cpp b/src/passes/RemoveUnusedModuleElements.cpp index 2ae03391b..358add76b 100644 --- a/src/passes/RemoveUnusedModuleElements.cpp +++ b/src/passes/RemoveUnusedModuleElements.cpp @@ -38,6 +38,7 @@ #include <memory> #include "ir/element-utils.h" +#include "ir/find_all.h" #include "ir/intrinsics.h" #include "ir/module-utils.h" #include "ir/subtypes.h" @@ -492,11 +493,36 @@ struct Analyzer { for (Index i = 0; i < new_->operands.size(); i++) { auto* operand = new_->operands[i]; auto structField = StructField{type, i}; - if (readStructFields.count(structField) || - EffectAnalyzer(options, *module, operand).hasSideEffects()) { - // This data can be read, so just walk it. Or, this has side effects, - // which is tricky to reason about - the side effects must happen even - // if we never read the struct field - so give up and consider it used. + + // If this struct field has already been read, then we should use the + // contents there now. + auto useOperandNow = readStructFields.count(structField); + + // Side effects are tricky to reason about - the side effects must happen + // even if we never read the struct field - so give up and consider it + // used. + if (!useOperandNow) { + useOperandNow = + EffectAnalyzer(options, *module, operand).hasSideEffects(); + } + + // We must handle the call.without.effects intrinsic here in a special + // manner. That intrinsic is reported as having no side effects in + // EffectAnalyzer, but even though for optimization purposes we can ignore + // effects, the called code *is* actually reached, and it might have side + // effects. In other words, the point of the intrinsic is to temporarily + // ignore those effects during one phase of optimization. Or, put another + // way, the intrinsic lets us ignore the effects of computing some value, + // but we do still need to compute that value if it is received and used + // (if it is not received and used, other passes will remove it). + if (!useOperandNow) { + // To detect this, look for any call. A non-intrinsic call would have + // already been detected when we looked for side effects, so this will + // only notice intrinsic calls. + useOperandNow = !FindAll<Call>(operand).list.empty(); + } + + if (useOperandNow) { use(operand); } else { // This data does not need to be read now, but might be read later. Note |