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Commit 98d8580c authored Oct 24, 2018 by Peter Collingbourne

Prevent clang from using the x18 register on arm64.

This is achieved via the compiler flag -ffixed-x18 for non-LTO builds
and the linker flag -plugin-opt -mattr=+reserve-x18 for LTO builds.

This change should be reverted once we upgrade past LLVM r340889
which does this by default on Android.

Bug: 112907825
Bug: 111759196
Change-Id: I05473ddbb98319d87d442425b4d715647eae3a38

parent ddfcd42b

cc/config/arm64_device.go

+5 −0

Original line number	Diff line number	Diff line
		@@ -25,6 +25,11 @@ var (
		arm64Cflags = []string{
		// Help catch common 32/64-bit errors.
		"-Werror=implicit-function-declaration",

		// Prevent use of x18 register.
		// TODO(pcc): Remove this flag once we upgrade past LLVM r340889
		// which does this by default on Android.
		"-ffixed-x18",
		}

		arm64ArchVariantCflags = map[string][]string{

cc/lto.go

+7 −0

Original line number	Diff line number	Diff line
		@@ -113,6 +113,13 @@ func (lto *lto) flags(ctx BaseModuleContext, flags Flags) Flags {
		flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-inline-threshold=0")
		flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-unroll-threshold=0")
		}

		if ctx.Arch().ArchType == android.Arm64 {
		// Prevent use of x18 register on arm64.
		// TODO(pcc): Remove this flag once we upgrade past LLVM r340889
		// which does this by default on Android.
		flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-mattr=+reserve-x18")
		}
		}
		return flags
		}

cc/sanitize.go

+7 −0

Original line number	Diff line number	Diff line
		@@ -471,6 +471,13 @@ func (sanitize *sanitize) flags(ctx ModuleContext, flags Flags) Flags {
		diagSanitizers = append(diagSanitizers, "cfi")
		}

		if ctx.Arch().ArchType == android.Arm64 {
		// Prevent use of x18 register on arm64.
		// TODO(pcc): Remove this flag once we upgrade past LLVM r340889
		// which does this by default on Android.
		flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-mattr=+reserve-x18")
		}

		if ctx.staticBinary() {
		_, flags.CFlags = removeFromList("-fsanitize-cfi-cross-dso", flags.CFlags)
		_, flags.LdFlags = removeFromList("-fsanitize-cfi-cross-dso", flags.LdFlags)