[WebAssembly] Change int_fast16_t to 32-bit

[ncw]

Summary

See: https://bugs.llvm.org/show_bug.cgi?id=35582

Since Wasm has to use 32-to-16 bit instructions to narrow values down, 32-bit should be a tad faster for operations needing 16 or more bits.

[dschuff]

lib/Basic/Targets/WebAssembly.h

108

I think we want least16_t to still be short, no? We do still support 16-bit shorts, so my interpretation is that the smallest type with width of at least 16 should still be 16.

[ncw]

lib/Basic/Targets/WebAssembly.h

108

...is there a way to do that? I couldn't find any other archs that do it; it seems like the stdint.h that Clang provides requires least16_t to match fast16_t. I copied this from the AVR target, although maybe that doesn't support 16-bit at all.

[ncw]

lib/Basic/Targets/WebAssembly.h

108

Sorry, now I see that AVR uses int because it has 16-bit ints...

There isn't any existing Clang target that uses 32-bit for fast16_t, so maybe it's currently not possible within Clang's framework (or at least, not without also fiddling with least16_t). lib/Frontend/InitPreprocessor.cpp hardcodes some logic with sets them to be the same.

I can abandon this review if that's not acceptable collateral damage (probably not, on reflection) - or could tweak InitPreprocessor.cpp and stdint.h to be more flexible (might need more review if you don't "own" those files?)

[dschuff]

lib/Basic/Targets/WebAssembly.h

108

I think it's worth trying to fix InitPreprocessor.cpp/stdint.h to remove the assumption that those types are the same. We'll need to get broader review, so it will be slower than if we were just changing our own files, but that's OK. If you're up for doing that I'd be happy to help you find reviewers, or otherwise I can take a shot at it; now is a good time since we're taking a closer look at our ABIs more generally anyway.

[ncw]

lib/Basic/Targets/WebAssembly.h

108

uhh... if you could take a look that would be great! I've only got a limited Wasm "budget" from my employer, and have to get back to customer work for most of the rest of the week.

Was there an issue I seem to remember as well, where Wasm32 was using "unsigned int" for SIZE_TYPE instead of "unsigned long".

[dschuff]

lib/Basic/Targets/WebAssembly.h

108

Yes, @sunfish is switching the wasm and asm.js ABIs to both use unsigned long.

[sunfish]

As @nw points out, clang's lib/Headers/stdint.h doesn't support this yet. Unless anyone feels strongly, I now propose we close this and just leave int_fast16_t/uint_fast16_t as-is.

lib/Basic/Targets/WebAssembly.h

private:
 
   const char *getClobbers() const final { return ""; }
 
   bool isCLZForZeroUndef() const final { return false; }
 
   bool hasInt128Type() const final { return true; }
 
   IntType getIntTypeByWidth(unsigned BitWidth, bool IsSigned) const final {
-    // WebAssembly prefers long long for explicitly 64-bit integers.
-    return BitWidth == 64 ? (IsSigned ? SignedLongLong : UnsignedLongLong)
+    // WebAssembly prefers long long for explicitly 64-bit integers, and int for
+    // 16-bit integers.
+    return BitWidth == 16 ? (IsSigned ? SignedInt : UnsignedInt) :
+           BitWidth == 64 ? (IsSigned ? SignedLongLong : UnsignedLongLong)
                           : TargetInfo::getIntTypeByWidth(BitWidth, IsSigned);
   }
 
   IntType getLeastIntTypeByWidth(unsigned BitWidth, bool IsSigned) const final {
-    // WebAssembly uses long long for int_least64_t and int_fast64_t.
-    return BitWidth == 64
+    // WebAssembly uses long long for int_least64_t and int_fast64_t, and int
+    // for int_least16_t and int_fast16_t.
+    return BitWidth == 16
+               ? (IsSigned ? SignedInt : UnsignedInt) :
+           BitWidth == 64
                ? (IsSigned ? SignedLongLong : UnsignedLongLong)
                : TargetInfo::getLeastIntTypeByWidth(BitWidth, IsSigned);
   }
 };
 class LLVM_LIBRARY_VISIBILITY WebAssembly32TargetInfo
     : public WebAssemblyTargetInfo {
 public:
   explicit WebAssembly32TargetInfo(const llvm::Triple &T,

test/Preprocessor/init.c

 // WEBASSEMBLY32-NEXT:#define __INTMAX_MAX__ 9223372036854775807LL
 // WEBASSEMBLY32-NEXT:#define __INTMAX_TYPE__ long long int
 // WEBASSEMBLY32-NEXT:#define __INTMAX_WIDTH__ 64
 // WEBASSEMBLY32-NEXT:#define __INTPTR_FMTd__ "d"
 // WEBASSEMBLY32-NEXT:#define __INTPTR_FMTi__ "i"
 // WEBASSEMBLY32-NEXT:#define __INTPTR_MAX__ 2147483647
 // WEBASSEMBLY32-NEXT:#define __INTPTR_TYPE__ int
 // WEBASSEMBLY32-NEXT:#define __INTPTR_WIDTH__ 32
-// WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTd__ "hd"
-// WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTi__ "hi"
-// WEBASSEMBLY32-NEXT:#define __INT_FAST16_MAX__ 32767
-// WEBASSEMBLY32-NEXT:#define __INT_FAST16_TYPE__ short
+// WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTd__ "d"
+// WEBASSEMBLY32-NEXT:#define __INT_FAST16_FMTi__ "i"
+// WEBASSEMBLY32-NEXT:#define __INT_FAST16_MAX__ 2147483647
+// WEBASSEMBLY32-NEXT:#define __INT_FAST16_TYPE__ int
 // WEBASSEMBLY32-NEXT:#define __INT_FAST32_FMTd__ "d"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST32_FMTi__ "i"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST32_MAX__ 2147483647
 // WEBASSEMBLY32-NEXT:#define __INT_FAST32_TYPE__ int
 // WEBASSEMBLY32-NEXT:#define __INT_FAST64_FMTd__ "lld"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST64_FMTi__ "lli"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST64_MAX__ 9223372036854775807LL
 // WEBASSEMBLY32-NEXT:#define __INT_FAST64_TYPE__ long long int
 // WEBASSEMBLY32-NEXT:#define __INT_FAST8_FMTd__ "hhd"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST8_FMTi__ "hhi"
 // WEBASSEMBLY32-NEXT:#define __INT_FAST8_MAX__ 127
 // WEBASSEMBLY32-NEXT:#define __INT_FAST8_TYPE__ signed char
-// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_FMTd__ "hd"
-// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_FMTi__ "hi"
-// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_MAX__ 32767
-// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_TYPE__ short
+// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_FMTd__ "d"
+// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_FMTi__ "i"
+// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_MAX__ 2147483647
+// WEBASSEMBLY32-NEXT:#define __INT_LEAST16_TYPE__ int
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST32_FMTd__ "d"
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST32_FMTi__ "i"
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST32_MAX__ 2147483647
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST32_TYPE__ int
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST64_FMTd__ "lld"
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST64_FMTi__ "lli"
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST64_MAX__ 9223372036854775807LL
 // WEBASSEMBLY32-NEXT:#define __INT_LEAST64_TYPE__ long long int

 // WEBASSEMBLY32-NEXT:#define __UINTMAX_WIDTH__ 64
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTX__ "X"
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTo__ "o"
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTu__ "u"
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_FMTx__ "x"
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_MAX__ 4294967295U
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_TYPE__ unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINTPTR_WIDTH__ 32
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTX__ "hX"
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTo__ "ho"
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTu__ "hu"
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTx__ "hx"
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_MAX__ 65535
-// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_TYPE__ unsigned short
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTX__ "X"
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTo__ "o"
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTu__ "u"
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_FMTx__ "x"
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_MAX__ 4294967295U
+// WEBASSEMBLY32-NEXT:#define __UINT_FAST16_TYPE__ unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_FMTX__ "X"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_FMTo__ "o"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_FMTu__ "u"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_FMTx__ "x"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_MAX__ 4294967295U
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST32_TYPE__ unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_FMTX__ "llX"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_FMTo__ "llo"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_FMTu__ "llu"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_FMTx__ "llx"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_MAX__ 18446744073709551615ULL
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST64_TYPE__ long long unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_FMTX__ "hhX"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_FMTo__ "hho"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_FMTu__ "hhu"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_FMTx__ "hhx"
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_MAX__ 255
 // WEBASSEMBLY32-NEXT:#define __UINT_FAST8_TYPE__ unsigned char
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTX__ "hX"
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTo__ "ho"
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTu__ "hu"
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTx__ "hx"
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_MAX__ 65535
-// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_TYPE__ unsigned short
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTX__ "X"
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTo__ "o"
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTu__ "u"
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_FMTx__ "x"
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_MAX__ 4294967295U
+// WEBASSEMBLY32-NEXT:#define __UINT_LEAST16_TYPE__ unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_FMTX__ "X"
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_FMTo__ "o"
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_FMTu__ "u"
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_FMTx__ "x"
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_MAX__ 4294967295U
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST32_TYPE__ unsigned int
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST64_FMTX__ "llX"
 // WEBASSEMBLY32-NEXT:#define __UINT_LEAST64_FMTo__ "llo"

 // WEBASSEMBLY64-NEXT:#define __INTMAX_MAX__ 9223372036854775807LL
 // WEBASSEMBLY64-NEXT:#define __INTMAX_TYPE__ long long int
 // WEBASSEMBLY64-NEXT:#define __INTMAX_WIDTH__ 64
 // WEBASSEMBLY64-NEXT:#define __INTPTR_FMTd__ "ld"
 // WEBASSEMBLY64-NEXT:#define __INTPTR_FMTi__ "li"
 // WEBASSEMBLY64-NEXT:#define __INTPTR_MAX__ 9223372036854775807L
 // WEBASSEMBLY64-NEXT:#define __INTPTR_TYPE__ long int
 // WEBASSEMBLY64-NEXT:#define __INTPTR_WIDTH__ 64
-// WEBASSEMBLY64-NEXT:#define __INT_FAST16_FMTd__ "hd"
-// WEBASSEMBLY64-NEXT:#define __INT_FAST16_FMTi__ "hi"
-// WEBASSEMBLY64-NEXT:#define __INT_FAST16_MAX__ 32767
-// WEBASSEMBLY64-NEXT:#define __INT_FAST16_TYPE__ short
+// WEBASSEMBLY64-NEXT:#define __INT_FAST16_FMTd__ "d"
+// WEBASSEMBLY64-NEXT:#define __INT_FAST16_FMTi__ "i"
+// WEBASSEMBLY64-NEXT:#define __INT_FAST16_MAX__ 2147483647
+// WEBASSEMBLY64-NEXT:#define __INT_FAST16_TYPE__ int
 // WEBASSEMBLY64-NEXT:#define __INT_FAST32_FMTd__ "d"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST32_FMTi__ "i"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST32_MAX__ 2147483647
 // WEBASSEMBLY64-NEXT:#define __INT_FAST32_TYPE__ int
 // WEBASSEMBLY64-NEXT:#define __INT_FAST64_FMTd__ "lld"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST64_FMTi__ "lli"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST64_MAX__ 9223372036854775807LL
 // WEBASSEMBLY64-NEXT:#define __INT_FAST64_TYPE__ long long int
 // WEBASSEMBLY64-NEXT:#define __INT_FAST8_FMTd__ "hhd"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST8_FMTi__ "hhi"
 // WEBASSEMBLY64-NEXT:#define __INT_FAST8_MAX__ 127
 // WEBASSEMBLY64-NEXT:#define __INT_FAST8_TYPE__ signed char
-// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_FMTd__ "hd"
-// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_FMTi__ "hi"
-// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_MAX__ 32767
-// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_TYPE__ short
+// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_FMTd__ "d"
+// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_FMTi__ "i"
+// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_MAX__ 2147483647
+// WEBASSEMBLY64-NEXT:#define __INT_LEAST16_TYPE__ int
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST32_FMTd__ "d"
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST32_FMTi__ "i"
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST32_MAX__ 2147483647
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST32_TYPE__ int
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST64_FMTd__ "lld"
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST64_FMTi__ "lli"
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST64_MAX__ 9223372036854775807LL
 // WEBASSEMBLY64-NEXT:#define __INT_LEAST64_TYPE__ long long int

 // WEBASSEMBLY64-NEXT:#define __UINTMAX_WIDTH__ 64
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_FMTX__ "lX"
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_FMTo__ "lo"
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_FMTu__ "lu"
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_FMTx__ "lx"
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_MAX__ 18446744073709551615UL
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_TYPE__ long unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINTPTR_WIDTH__ 64
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTX__ "hX"
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTo__ "ho"
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTu__ "hu"
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTx__ "hx"
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_MAX__ 65535
-// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_TYPE__ unsigned short
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTX__ "X"
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTo__ "o"
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTu__ "u"
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_FMTx__ "x"
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_MAX__ 4294967295U
+// WEBASSEMBLY64-NEXT:#define __UINT_FAST16_TYPE__ unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_FMTX__ "X"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_FMTo__ "o"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_FMTu__ "u"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_FMTx__ "x"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_MAX__ 4294967295U
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST32_TYPE__ unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_FMTX__ "llX"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_FMTo__ "llo"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_FMTu__ "llu"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_FMTx__ "llx"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_MAX__ 18446744073709551615ULL
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST64_TYPE__ long long unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_FMTX__ "hhX"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_FMTo__ "hho"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_FMTu__ "hhu"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_FMTx__ "hhx"
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_MAX__ 255
 // WEBASSEMBLY64-NEXT:#define __UINT_FAST8_TYPE__ unsigned char
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTX__ "hX"
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTo__ "ho"
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTu__ "hu"
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTx__ "hx"
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_MAX__ 65535
-// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_TYPE__ unsigned short
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTX__ "X"
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTo__ "o"
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTu__ "u"
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_FMTx__ "x"
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_MAX__ 4294967295U
+// WEBASSEMBLY64-NEXT:#define __UINT_LEAST16_TYPE__ unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_FMTX__ "X"
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_FMTo__ "o"
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_FMTu__ "u"
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_FMTx__ "x"
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_MAX__ 4294967295U
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST32_TYPE__ unsigned int
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST64_FMTX__ "llX"
 // WEBASSEMBLY64-NEXT:#define __UINT_LEAST64_FMTo__ "llo"