diff options
Diffstat (limited to 'llvm/lib/Target')
| -rw-r--r-- | llvm/lib/Target/WebAssembly/README.txt | 16 | ||||
| -rw-r--r-- | llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp | 12 |
2 files changed, 28 insertions, 0 deletions
diff --git a/llvm/lib/Target/WebAssembly/README.txt b/llvm/lib/Target/WebAssembly/README.txt index 3be7007a57f..3433b1553e8 100644 --- a/llvm/lib/Target/WebAssembly/README.txt +++ b/llvm/lib/Target/WebAssembly/README.txt @@ -150,3 +150,19 @@ Add support for mergeable sections in the Wasm writer, such as for strings and floating-point constants. //===---------------------------------------------------------------------===// + +The function @dynamic_alloca_redzone in test/CodeGen/WebAssembly/userstack.ll +ends up with a tee_local in its prolog which has an unused result, requiring +an extra drop: + + get_global $push8=, 0 + tee_local $push9=, 1, $pop8 + drop $pop9 + [...] + +The prologue code initially thinks it needs an FP register, but later it +turns out to be unneeded, so one could either approach this by being more +clever about not inserting code for an FP in the first place, or optimizing +away the copy later. + +//===---------------------------------------------------------------------===// diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp index 50ee79b7079..41249117ae0 100644 --- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp +++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp @@ -31,6 +31,14 @@ using namespace llvm; #define DEBUG_TYPE "wasm-explicit-locals" +// A command-line option to disable this pass. Note that this produces output +// which is not valid WebAssembly, though it may be more convenient for writing +// LLVM unit tests with. +static cl::opt<bool> DisableWebAssemblyExplicitLocals( + "disable-wasm-explicit-locals", cl::ReallyHidden, + cl::desc("WebAssembly: Disable emission of get_local/set_local."), + cl::init(false)); + namespace { class WebAssemblyExplicitLocals final : public MachineFunctionPass { StringRef getPassName() const override { @@ -164,6 +172,10 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) { "********** Function: " << MF.getName() << '\n'); + // Disable this pass if directed to do so. + if (DisableWebAssemblyExplicitLocals) + return false; + // Disable this pass if we aren't doing direct wasm object emission. if (MF.getSubtarget<WebAssemblySubtarget>() .getTargetTriple().isOSBinFormatELF()) |
